Some people are attracted to celebrities, no matter how small their celebrity, because it might feel like it is the closest they will ever get to someone famous enough to appear on TV. In addition, they might actually like the person.
I think some people feel like they aren’t much. It makes a big deal to them to know someone that a lot of other people know. It makes them feel almost next to being famous. Perhaps there is a kind of halo effect. We’ve had questions like that here, where people ask if you have had any meetings with famous people. It is kind of cool when it happens, I think, for a lot of people.
I could speculate further, but really, it’s just speculation. I don’t know if you would even get a satisfactory answer from someone who was one of these people. It’s hard to imagine them having sufficient powers of introspection to tell a convincing story. But I think, to boil it down to one word, it’s status.