This is a non sequitur, but I don't know. I don't. I think the reason is people aren't used to eating plants and find the tastes and textures disagreeable. It's a taste that can be acquired at any time, though. I stopped eating meat for ethical reasons, but I'd only go back if I was literally starving. Vegetables taste so much better, but you need a cuisine that does vegetables properly, like Indian or Mexican. Trying to do a bland cuisine like American or British without meat isn't going to be a good time.