Regarding buying food on an airplane, what about the effect of simple politeness? I'm not sure I would call it "peer pressure," when I feel uncomfortable about

Regarding buying food on an airplane, what about the effect of simple politeness? I'm not sure I would call it "peer pressure," when I feel uncomfortable about eating food next to someone who doesn't have any. Maybe it's a cultural thing, but I would rather wait to eat until the person next to me also has food. Once I was on a train, and the woman next to me offered to share some of the sandwich she brought with her. I said, "no thanks, I was about to go get some food from the dining car." I got my own sandwich and brought it back. I understood completely what was behind her offer, and I am sure we both felt more comfortable eating together, even though we didn't know each other and would never see the other person again.