Why do we like celebrities? and why do we copy them?

Because celebrities are artists, and art is what forms culture, and culture is something we all need to feel like we belong. So in other words, it's because us humans are weak and fear loneliness.

Because they got power, money, influence, and general attention. People want to strive to be something, and these are their role-models. These are the idea for them of "success." So, the simple equation: They relate to them, they see them as "heroes," role models, and they believe in some point that by worshiping them, they might gain their grace. Or something like that. Anyway, you can have a picture of a society by what their "heroes" look like. In the past you had savage warriors, today you got dipshit singers that sing about bullshit that everyone buys. Well, people gain distraction from it, have a common basis to become friends "I like X too!" And, just have whatever to make them feel that they are a part of something. So, it's all dumb-ass followers wanting more.