You're missing something. They're not insane, and neither are you.
Imagine you've loved a certain musician your entire life and you could pay them to sing a song with your name in it.
Or, imagine you and your spouse saw a certain movie on your first date, and you think it would be funny and thoughtful to have one of the actors (or characters) from that movie wish your spouse a happy birthday.
Or, imagine you have followed a sports team for years and have the opportunity to talk to one of the stars.
There is nothing strange or new about celebrity. Touching fame is interesting and exciting to people. There are celebrities who are genuinely meaningful to people -- maybe their work helped get through a tough time.
You don't have to understand it, but it's not hurting anyone, so there's nothing insane about it. It's just a form of personalized entertainment.