Because they are arrogant liberal turds who think they know it all. They do nothing but lie and lie and lie. All the while, they have the hide to take a sanctimonious view over others.
Because in their world, their voices seem important, or at least no one has ever told them that it isn't. Since many entertainers are only educated in their craft, they unsurprisingly lack rationality when it comes to political commentary. All they know is that they have a lot of wealth, and that poor people don't, so advocating that the government use force to do something about it, is their way of "doing something compassionate".
They get so conceded because of their fans. Some people think these celebrities are special and above the average citizens. It's all ridiculous to me but I dont watch TV and most of these new celebrities I've never heard of.