The guys at pandora understand the junk culture that exists today so they only play the junk music artists. That may seem "stupid" to the amateur layman but it is actually pure business genius.
You can only make money in catering to the mainstream market, no matter how dumb that market might be. The music illiterates that pandora favors on its playlists are trendy and cool and young and good looking -- and most importantly, the kids love the junk music the most.
So pandora has no pretensions to promote "great artistic music," most of which never sells in our society today. Beethoven, if he were promoting himself today, would be the kind of music that kids flush down a toilet.
That kind of strategy in addressing the cool and dumb will payoff huge in $$$ profits, just sit back and watch this beauty hit $30 a share before year's end.