We no longer breed dogs to be good hunting partners. Well, some dogs are still bred for this purpose, but only a minor part of their overall population. Others are selected for various aesthetic tastes. That is because we no longer need the dogs as much as we once did. Cats were not that much needed to begin with, so their breeds are as varied, I suppose.
Horses have (somewhat) avoided such fate only because it’s harder to keep one as a pet in a multi-apartment building.
What happens when we no longer need our bodies as much as we do now? Either we upload and live incorporeal or we take robot bodies. Or even flesh bodies, but without being in life-long relationship with them. In short, if we could afford experimentation with the flesh. Of course, some people will choose to live proper biological lives, continuing ancient birth-life-death cycle. That’s analogous to how some dogs are still true to their ancient hunting and guarding purpose. But most other human bodies will be free to play with.
We’ll either breed or engineer various body shapes and biologies for our mind to occupy. I could be an aquaman for a weekend, take tough savage-giant body for extreme vacations in tundra, rent an eerie slender man body for Halloween party, take an overweight balding dwarf body to live in for some years just because why not. There could just as well be vogues which the majority would follow. There could be competitions for the most high, strong, fast, durable body. Beauty contests will take a new aspect to them as well.
As with our pets, we won’t abandon our bodies. Though by not being so essential they will be up for a very different treatment.