Well yes, that's kind of my question. If the world went Vegan, there would be no motivation for anyone, except perhaps a few zoos, to keep cows and chickens alive.
Who knows what would happen in the oceans without fishing.
Would nature just take over and create a new disease to kill off the weakest?
FWIW, I guess you'd like my neighbor who just lets his cat run free all the time. I don't know how it can even be classified as a "pet"?
We have coyotes and foxes running around here. Surprised a cat can survive.
Just my opinion, of course.