This is a very interesting question. What makes “ordinary” people want pictures of themselves with or autographs of “famous” people?
I have always been a bit star struck. I am not an auto/photograph hound, but to the celebrities who have meant a great deal to me, or have moved me, it is a nice memento.
It is also an historical document that this person and I have been in personal contact. Or if the person is deceased, a record that this person had actual contact with this paper that they signed.
I had the honor of working, briefly, with both Bob Hope and George Burns as a young’un and I can tell you I wish I had a camera with me back then.
It is a very odd phenomenon, but something I can totally understand.
PEACE.