Well there must be a reason they don't have vegan menus, don't you think? How many beets does a steak place use? If they had to cater to vegan people, they may have to order more. If they don't sell, out in the garbage it goes.
I'll be totally honest here. I don't know much about vegan food. Never cared to learn either because I eat what I want and don't consider my health in the process. If I feel like eating Big Macs all week, that's what I eat. So if the list you gave me is something anybody can put together because they already have the ingredients, what are these vegan customers complaining about in the OP? Is there good vegan food and bad? I'm not making an argument, but since you eat the stuff, I'm assuming you would know.