Radio Station Playlists

So, US99.com now has a list of the songs that they've played in the last 24 Hours... which is nice... except they're not playing songs by Artists that deserve to be played. It's annoying when you turn on the radio and the same song is on 2 hours after you just heard it. Is there really so little music out that Radio stations can't play something more recent. I don't mind the songs from like 10+ years ago, it's nice to hear them once in a while. But there are some songs that are new, and they've played before, but now all of a sudden it's no longer played... what's up with that?