Because some stories are about fantasy and some stories are about exploration.
Bojack is about exploring what happens when you achieve a hedonistic lifestyle. Most American media is about winning the fortune, achieving fame and glory, getting the girl.
Even if it isn't even close to the real situation, which I wouldn't know, Bojack presents a clear set of characters and starting positions and showcases the results.
As an American, I'm aware that there's something wrong with the rich and famous. They have high suicide rates, anger issues, obsessive personalities, and I'm wondering how they could have everything and still want more. Bojack answers that question in a satisfying, if not honest, way.