Why do you need to tell people you’re vegetarian if want a meat-free breakfast?
at a guess
i don’t want what you are offering = fussy bugger, get bent.
I can’t eat what you are offering = oh you poor soul I’ll knock you up something special.
the fact that being vegie/vegan is mostly just being a fussy bugger* (just as in junkyards example, meat eaters turning their noses up at slugs and cockroaches) doesn’t seem to come into it.
*yes there are valid moral/ethical issues but veggies generally are fully able to eat and digest meat/dairy unlike lactose gluten etc intolerances
<edit> but I do agree “I’m a vegie who eats fish” should earn you a slap in the face with a wet fish. My sister tried that one, a certain amount of mockage ensued.