This seems a little confrontational, but I could very well be reading your intention wrong.
My son, actually, had so many protein allergies at birth that we couldn't identify them all. We are very thankful to God that he has outgrown them (infant protein allergies are normally temporary, but not always). I was that mother who had to bring safe drinks, food, and snacks everywhere we went. I was the mother who wondered if my son would ever be able to eat pizza like most other kids, he couldn't even have cake his first birthday because we didn't have enough identified safe ingredients to make an allergy free cake. I've stressed over things like if a theme park would let us bring in the food my son needed (not Disney World) or if I would have to waste precious park time defending my son's needs to customer service.
I was referring to why most people bring in coolers, I'm very aware people might need coolers for things like medically necessary food or medication, but they are a small fraction of those who bring in food and drinks. I, also, think Disney's policy on the issue is great and much more customer friendly than some of its competition.