The robots on the star cruiser Axiom do everything for the humans -- they clothe them, they feed them, they carry them from place to place on completely automated scooters, they clean up after them, and they maintain every aspect of the ship's operation. People don't even speak to each other except via computer screens projected directly in front of their faces, even if the person they're speaking to is sitting right beside them. That last sentence is less a biting commentary on the current trajectory of the human condition and more an agenda-free narration of a bunch of friends staring at their iPhones while sharing a booth at Applebee's.
But then WALL-E comes in, shakes everyone out of their glazed hedonism, and takes the reinvigorated humans back to Earth to slowly rebuild society.
The Dark Implication:
The robots on the Axiom have been taking care of the breeding as well.
Think about it -- the people on the Axiom are so large, they literally cannot move under their own power. They're essentially giant upended turtles.
Had WALL-E not come along, this man would have wobbled there until he died.
They're terrible at speaking with each other, which we see when John and Mary accidentally touch hands and are forced to hold what is likely the first personal conversation anyone on that ship has had in 700 years. Even if they could fumble their way into a romantic relationship, no human being on the Axiom is physically capable of actually having sex -- either they'd have a massive heart attack or their skeletons would collapse from the effort.
"At this point we're not sure if you even have external penises anymore."