Why is the music on television and mainstream radio stations really lame, most of the time?

Loads of this mainstream music is really lame most of the time and gets forgotten about really quick, why do they give exposure to people who will just flop like Jojo, Ordinary Boys and Ozone when there are real bands and musicians out there who are withstanding the test of time and make far better music, Slipknot, Weird Al Yankovic and some rappers but this is because of their controversial lyrics although the censorship is a bit annoying,