There is no evidence for this, but I reckon because they are absolutely brilliant to persuade people in order to like them and/or to have "sponsors". However, there are maybe some "fans" who are untentionally ignored by the celebrities due to their massive numbers, or perhaps just a complete jelousy, or utterly madness? Which is which, I don't know. :D
Personally, I have nothing against them. Let's pick, Justin Bieber for example, I don't like him initially, not because for who he is, but because of his music. It's not my cup of tea tbh. It's like I am eating a box of chocolate, but I love his personality. He is so humble, so genuine and kind and he is driven to achieve his goals. He deserves everything he has I have to say.
To put it simply and crudely, people are not fair!