Some don't like the unhealthy aspects of animal protein.
Some don't like the taste, or smell of cooking flesh.
Some hate the greasy and fattiness of cooked flesh.
Some just hate dead animals on their plate, and , much the same as you'd make a kitty litter cake, or a centipede cupcake for Halloween, might want to eat something for fun, without the actual "Stuff".
I mean, most people would eat a bunny rabbit shaped chocolate LIndt for easter, or meat eaters would eat a finger shaped piece of fish, but would they actually eat a finger? Or how about a wheel shaped burger? Or a ping pong ball shaped ball of meat? See my point?
Vegan is a lifestyle, and technically means to abstain from the exploitation of anything that comes from an animal. Food or Clothing, products etc. It says nothing about using the animal form to take delight- such as a cake shaped as a ladies' ***.
Vegetarian simply means, to not eat animal flesh.
The more you read, the more you know.