Because they aren't vegans. They are vegetarians. It's not that they won't eat meat and fish and dairy because they're tree-hugging animal lovers. They don't eat meat because a) they don't like the taste and/or b) (for your case) meat contains high cholesterol amongst other harmful things. Whereas tofu cooked with meat, and that harvest morning/gardenburger stuff is healthy, has little to no cholesterol.. These things are also surprisingly high in protein so you aren't really missing out on much of the nutrients.

And I guess c) people dont like the idea of eating animals. But they don't mind the taste. But thinking about eating flesh turns alot of meat eaters into veggies.

PS. I love meat. mmm meeat.