Well, how would it work? You'd have to have a bit of the animal that would be separate, detached from the other bits. But then how would that bit get nutrients and oxygen?
Also what good would it be? Most terrain is unsuitable for wheels. That's why we build roads.
Also, what would it evolve from? If you're talking about "animals we can pet and cuddle with", that would be vertebrates, right? Well, where are the potential precursors to a wheel in vertebrate anatomy? How would they replace legs?
Because its a bad idea, you need roads and level sturdy terrain for wheels to fully deliver their potential. You would need heavy regeneration abilities on your wheels, because of tare out doing bends, cars have heavy duty rubber wheels, reinforced whit steel wire and you still need to switch them out, how well do you think skin or bone would fair. Then there is the whole problem of how do you keep the wheeles supplied with blood, any vains would just tare out after one spin.....
Christianity, One woman's lie about an affair that got seriously out of hand
What are the Christians gonna do to me ..... Forgive me, good luck with that.
Because its a bad idea, you need roads and level sturdy terrain for wheels to fully deliver their potential.
Reminds me of Papua New Guinea even in recent history. The terrain is so steep and mountainous that the wheel was never widely adopted. All communication and travel was based on narrow footpaths so there was very little trade between villages to the extent that each village developed it's own language.
I'm talking about animals we can pet and cuddle with.
Dictyostelium discoideum (AKA slime mold). Cute and cuddly is in the eye of the beholder. Dictyostelium discoideum can aggregate and move around like a tank tread.
Birds, Bats, flying insects don't have propellers, but when is the last time you saw an airplane alight on a tree twig or electric wire?
Saurischian dinosaurs have an axle-in-casing hip joint structure - the legs can swing front-to-back but not side-to-side or twist like our ball-in-socket hip joints. You couldn't outrun a T-Rex but you could outmaneuver him/her/it.
How come evolution never came up with the wheel and axle?
Why should it?
Are you expecting evolution to devise every conceivable answer to every conceivable issue? Good enough is good enough for evolution. Compared to wheel-and-axle solutions a pair of limbs (or many multiple pairs) were, apparently, quite sufficient a body plan that no other structure proved to be as advantageous for those clades of organisms.
So the answer may be as simple as saying a wheel-and-axle never developed because a number of more than adequate solutions had already been put into use.