They already are, at least the most menial forms of labor. I go to the supermarket and there are automatic cashiers now. I go to vending machine and buy food on the spot that was previous assembled by a machine in the first place. There are buildings that are
quickly assembled in a factory and put together on the spot, very little manpower required.
This is mostly stuff that could have been done by humans (and probably better by humans), but getting rid of the humans from the process is more economical. Now this type of automation is at the very heart of computer science (and a huge interest of mine).
And we are moving towards BETTER automation techniques, so we can do more with it, and cheaper too. The eventual goal being general intelligence, at that point humans need not about any work at all - intellectual or otherwise, they'd be outclassed by computers
anyway even on things like R&D.
All this is primarily a software problem, and a huge one at that... but there is no reason to believe it won't happen.
And we are already making progress to it anyway. It's nothing we can't solve, Turing knew this. Humans can do anything a Turing machine can do, and nothing more. Seeing how small and low power the human brain is, it's quite likely that an artificial intelligence
will reach a level on intelligence not even the most savant people in history have achieved.
Now, it's time to use our brain power to realize the more economical enery production system!
That will save this planet, Earth, and all of us!