I thought you would never ask!
Sarcasm aside, I find myself frequently telling people that I brought my own food along with me since I shouldn't expect to be able to eat anything that anyone else has prepared. Why do I torture myself like this when delicious entrees are thrust in front of me? Well, because when you prepare your own food, you know how you made it and what you put in it. If you're on a crazy diet like I am, knowing every ingredient is crucial to maintain my sanity and prevent abdominal discomfort. But, it's a little difficult to refuse food without being rude. I explain my food problems, and usually people understand, but I still feel rude asking another person, "Are there onions or garlic in this? Are you sure? How about milk? Oh and I can't have spicy things either." To avoid this issue, I bring my own food. That way I don't go hungry, I don't feel like I am insulting another person's cooking abilities, and my guts can rest in peace.