Honestly, I know too many people who know I have food allergies, but don't hesitate to refer to people with food allergies as "freaks" in conversation with me. They're also irritated by things like having to bring fruit instead of cake to their kid's soccer games because one of the teammates can't have anything with gluten. As if the kid was making it up just to deprive his friends of some cake.

So if I start asking at a buffet about ingredients, I expect to run into people who are annoyed by it. Even if they're polite to my face, they're thinking I'm a PITA.

I do think someone with dietary restrictions needs to take responsibility as much as possible. It's just easier to assume there will be nothing you can have on the buffet table, and provide your own food.