Maybe because all the other robots were stupid… 
Because their eyes were way too big, they got blinded by the sand storms and couldn’t find their recharging stations!
I just think there was a type of “kill signal” because if sand storms wiped them out, they would be laying around, severly damaged. But the robots look like they were in the middle of working.
i kind of like the idea of all the wall-e’s dying slowly…i think the gradual loss and inevitability of loneliness brings a lot of extra depth to wall-e’s character.
I was under the impression that they simply broke down over time. WALL-E, being probably the only one who could think rationally has simply lasted as long as he has by constantly repairing himself using the dead WALL-E’s for parts.
At the beginning of the film, you can see lots of other broken waste disposal machinery in the background. My theory is that after the WALL-E’s collect and cube the waste, it is then taken away in trucks (like the one WALL-E lives in) and disposed of. You can see these trucks and large conveyors at the beginning of the film.
Since none of this is working any longer (and therefore the chain of events has been broken), WALL-E simply started to stack the waste cubes into giant towers, since he was only programmed to do this. There was simply nothing left to complete the cycle and take the waste away.
It kinda shows that a computer will only do what a computer is programmed to do. Despite WALL-E developing a personality, he is still following his original programming - oblivious that his efforts are wasted. After all, the film is about breaking routines… and that innocence is what makes him cute 
I agree with the sorta “signal” thing… I mean that’s the only plausible idea and like A113 said : "Well WALL•E didn’t feel bad for them, as he was constantly taking their parts to survive. I think all those other WALL•Es were turned off before our WALL•E developed a personality. "
I would be more inclined to believe in the “kill signal” theory, because it doesn’t make too much sense to me that WALL•Es would start breaking down, especially when you think about how many times WALL•E got hurt. It would also help to know of exactly when WALL•E started developing a personality - if it was before (or during) a time when other robots started to break down, maybe the reason why he was the only one to “survive” was because he started to take bits and pieces of the already broken down robots, so he never really broke down. Just like if you keep a car in good condition, it could last a long time if you keep replacing its parts.
But if we look into the “kill signal” theory, why didn’t the signal affect WALL•E? I don’t think any humans would have physically attended Earth to manually shut down the robots because it would have been too risky and maybe even poisonous because of all the pollution, and later on they built a robot (EVE) to do the job of attending the Earth, but for a totally different task.
As someone previous to me brought up, maybe it was his personality that overode that command - his desire to survive was greater than its desire to obey a life-ending command. But if that is the reason why the signal didn’t affect him (his personality), that reason wouldn’t match with the timeline, which is: WALL•E developed a personality because he was alone, and with no other robots (well, they were there, they just weren’t “alive.”)
But a signal could still have been sent out, it’s just that maybe at the time it was sent out, WALL•E was somewhere that the signal couldn’t reach him, kind of like a bomb shelter, I don’t know. Also, the WALL•Es that were affected by the signal were shut down mid-task, like in the middle of gathering garbage so that would support the signal theory further.
But both theories are reasonable, and it’s really interesting to speculate even if we might never know. I don’t think I would take the video game as canon, though.
They probably got a kill signal from BNL when they decided operation cleanup was a disaster. It’snot the environment because the other walles look like they were in the middle of working when it happened. Oh and when AUTO was showing the captain when the Axiom received the message about A113 one message had one error, unlike the others. Maybe that’s our one walle who refused to deactivate for some reason.
They went thru those msgs so fast, it was hard to see. Could Wall-e have been able to transmit a ‘Failed to Shut Down’ message back somewhere in the city to a relay station, that then transmitted to a satellite, which then transmitted to the Axiom? I doubt it. I just don’t think that Wall-E, out of the other 700,000 of his kind, was very important to them. Only if they were afraid that the robots would go off half-cocked and build skyscrapers in the wrong places, or even out of non-garbage, is why they might want to shut them all down.
Someone said the ultimate plan was to unload the big stacks with the conveyors and then incinerate them somewhere. But then you have toxic gases and carbon dioxide and waste ash several feet deep all over, even worse than sandstorms.
Also, with what RachelCakes said. “…bomb shelter” ?? I would think more like a tunnel where Wall•E might have missed the shut down msg, just like in the Axiom when the one guy couldn’t hear the other and said “I can’t hear you, I’m in a tunnel!”
Guys, if you show me how t put some type of image into a post, I could show you the one that had the one error.
First, host the image on an image-hosting site such as imageshack.us . Then browse to said picture on your hard drive, and copy the link it gives you. Then wrap the image in tags and presto!
By the way, the “kill theory” makes some sense to me. I mean, maybe WALL•E just didn’t get it or something, or perhaps a malfunction occurred in his AI/structure.
This is the pic, hope link works. Actually, if you look closely, there are “two” errors.
img129.imageshack.us/my.php?imag … re1mn7.png
Oh wow. One error. I wonder what that was referring to. If it was indeed the error that 'cause one robot to not be switched off, then that’s pretty darn clever of Pixar to think of that and put it into the BnL quarterly report.
And no-one has brought up the fact that WALL•E may have been created with a malfunction, so he didn’t pick up the signal that told him to switch off, or he was able to override it, or something. Good thinking, Remy14. This may also be the malfunction that lets him develop a personality, too.
Well, I didn’t read all the replies because of the lack of my time, so excuse me if I repeat someone’s idea.
The most plausible theory for me is that all the Wall-es were switched off and the only one, always neglected and abandoned, was again forgotten to be turned off (so, does anyone still dream about eternal life?). It comes clear that they didn’t break up, if to take Eve’s reaction into consideration. If Eve was programmed that there were some creatures on the Earth, she’d probably not react in THAT way. I think, BnL wanted to have more power over the mankind, so it tried to prevent the Earth to be cleaned and the people to turn back home.
I don’t know anything about the game - I have absolutely no will to play it. I’m overwhelmed by the movie - nothing more to add
Actually I found 3 errors on the status report (click to enlarge.)
So that’s errors in 2101, 2103 and 2108. Anyone want to speculate on what those errors were and why there were three of them, and not just one?
Firstly, good catch, coolio2654! Well done on noticing the error!
Secondly, Rachel, I guess the errors could be other cases of WALL-Es that weren’t shut down. There were WALL-Es all over the world, right? So, there’s a chance that a couple other WALL-Es had the same error that the WALL-E we know had, and didn’t shut down. We just never got to know about them because they might have been destroyed by the environment anyway, and the film was only really set in one part of Earth.
Then again, the other errors could pertain to something entirely different. Other machinary, perhaps- it’s difficult to say.
And another thing, what happened to all those giant incinerator-bots mentioned in the director’s commentary? You think that there would be at least 1 dead one in Wall-e’s city.
lizardgirl - What if… there were other WALL•Es that developed personalities too, but they lived in different countries?!
Then we can find matches for all the other EVEs. 
Ha, ha. Yeah, pair 'em up. 
Seriously, I don’t think the other EVEs would be interested in dating, unless, like EVE, they had a malfunction, too. I think EVE had a malfunction, like WALL•E, so that’s why they could love.