Out where I live, you either listen to Rock/metal, Rap/hip hop, or you listen to country. Almost everyone listens to bluegrass and other folk music (I live in kentucky, dont give me that look, its good music, some of it anyways.)
I think the reason most "mainstream pop" is big is because it gets played nonstop on the radio and in clubs. I dont think very many people actually listen to it to "listen". Most of them use it as background noise in clubs, shopping malls, kids centers, etc. Not to mention thats the music most likely to be used on commercials or TV shows. These places have to pay for the music too, and theyre gonna pay a lot more than some random person in Walmart, so maybe this kind of schews how much of each music is played.
The other thing is that very few people like to admit they listen to "mainstream" music. It carries a huge negative association, and tends to imply something is "bad" or lacks quality. For example, Nirvana was mainstream during the 90's. Argue all you want, but they had a platinum album, radio hits, and were known almost everywhere. Yet no one will call them mainstream, because people still like them (including me, just using them for the sake of argument). Same thing for Led Zeppelin, Pink Floyd, AC/DC, Rolling Stones, the Beatles, The Who, Metallica, Iron Maiden etc. They're all "mainstream" in the sense that they were big back in the day (some even to this day) and had huge top 40 hits, yet no one would possibly call them "mainstream" music these days. If you want to get really technical, almost any popular band or artist is mainstream, even many "indie" bands. Mainstream is such an ambiguous term theres no real point in even using it at all. I just say that I listen to rock, metal, and folk, and leave it at that. However, when most people say "mainstream", they mean Justin Beaver, Hannah Montanah, Britney Spears, etc. They use it to imply music that is popular despite the fact that they hate it. At least, thats the way my friends use it.
Me personally, I listen to tons of classic rock and early metal, as well as folk and bluegrass as I work at a local folk music radio broadcast station. However, I'm a guitar teacher, so I use a ton of this early music to show kids I teach where their favorite styles came from. Nothing is as satisfying as showing a kid that his favorite modern metal band learned their tricks from a Black Sabbath album released almost 40 years ago.
