BA is usually awesome (but I love Heathrow too).

I guess it's that thing where people think "oh, I'll just ask him to get a picture with me. No big deal, right?" so everyone constantly asks because they see their own actions as a mild inconvenience, but all together (and especially at times when a celeb is trying to be inconspicuous/asleep/whatever) it could drive someone insane, even if they were a complete saint (and worth 200 mil).