Because people like the taste of meat and at the same time don't want to hurt animals. They also want to maybe cook the same kind of food but without animals. What's wrong in that?
The fact that veganism is not about solely harming animals, it is a philosophy which encompasses a wholesale rejection of animal subjugation; this includes suffering yes, but it also includes commodification and exploitation en masse. It is ethically extremely questionable to claim that you support animals, but to want to pretend to eat them.