Why do fans go into hyper mode when it comes to their favorite stars?

I'm a lowkey fan. I don't get overly excited at the mention of someone's name. It just not me and I don't quite understand anyone who gets all starstruck at the mere mention of a person's name.

So, I put the question out there:

Why do some people get excited and can't breathe at the mention of their favorite celebritie's name?