well, this is just speaking for me, but i do because it opens up my diet to variety: there’s lots of recipes that have meat in them that i’d like to try, and tofu or tempeh just doesn’t always work as a substitute ingredient. it helps give me options when going to a barbecue at a friend’s place to bring my own meal. and, if it gives me options and flavor and doesn’t involve the slaughter of an animal, where’s the harm in it?