Thats interesting, I see what you're saying, although its actually the other way round in the biology world, signing your book for someone is considered a mark of respect for the person you're signing for.
I don't know what field you work in, but in my line of work I have heroes and I've asked them to sign their books for me, and when I work with them or in their line of sight I pull out all the stops to do the best job I can. I don't know why footballers should be any different