People respond well to messages that confirm what they already believe, and they actively seek out that kind of media. In America in particular, we believe we are entitled to attention, personal wealth, and lots and LOTS of regular, active, acrobatic sex. So, self-centered media stars saying "Me me me, look at my sexy body and how awesome my life is just because I wanted it to be" are more popular here than they ever have been.
It's hard to really nail down the actual causal relationship there, though. Is American media promoting self-entitlement because we actually are self-entitled, or vice versa?