I have had that happen. I approach homeless people often and ask if they are hungry and offer them food. I ask “what would you like” and they usually say just a hamburger. I go the distance, a grilled chicken sandwich, fries, a salad, and a glass of water. They are shocked when they get it. When they respond “I am vegan,” I say “starve, you are not going to make it off the street by demanding food your way.” It is a gift and now they want to be specific? Get real!
Actually, there are a few reasons why homeless people go vegetarian.
1) While they could eat fast food, even after a few weeks it tends to make you sick. So they go out of their way to avoid meats and grease. Wave a burger under their nose and many have to choke back vomit.
2) Vegan food lasts a lot longer, for the most part, and when it spoils it doesn’t go off with bad bacteria. A canister of generic rolled oats has about 30 - 2 cups prepared meals in it.
3) Of course homeless people tend to smoke, do drugs, and drink alcohol, and eating vegetarian helps to mitigate a lot of the problems of an unhealthy lifestyle. Many also eat that way to “clean up” after quitting the bad stuff.