But the mineral water and the salad don’t necessarily need to be labeled as vegetarian. I think the issue is that people don’t interpret the ‘vegetarian’ label

But the mineral water and the salad don’t necessarily need to be labeled as vegetarian. I think the issue is that people don’t interpret the ‘vegetarian’ label on the menu as “this is OK for vegetarians to eat”, they interpret it as “we altered this dish to make it suitable for vegetarians”, and usually the latter means it’s not very good.