[Beerinkol]

Because people tend to make a big deal out of it. It's like the old joke that goes "How do you know if someone is vegan or not? They'll tell you." Probably because communal eating is a popular cultural activity which most people participate in several times a day and it's not politically correct to berate food allergies which are very, very common. If preparing or sharing a meal it's simply good practice to inquire about dietary restrictions. In the end it's about respecting peoples preferences and not taking it personally. For some reason we would never expect people to listen to music or wear cloths they don't like but we expect it when it comes to food? As a cook I'm very proactively vocal about what goes into what I make especially if it contains something that may be problematic to someone.