Try this little excercise: walk over to the person nearest you and ask them what kind of music they listen to. If they say something like "Oh, I listen to everything" or "I like a mix of different things" I want you to bow down and worship at the altar of my genius. One of those two responses is the answer you'll get from 90% (totally valid and heavily researched percentage by the way)of people when you ask that question. I'll even go so far as to say that 100% of those people are lying directly to your face. No one listens to "everything". Find me someone who has pop, rap, bluegrass, zydeco, acid jazz, Gregorian chant, blues, classical, afro-punk, funk,soul,techno, 70's rock,country, and shoegaze on their iPod and I'll show you a avocado made from oranges.
Most people like one or two types of music and a couple of additional artists that are mainstream forms of various musical styles. For instance if you love Christina Aguilera, Kanye West, and Linkin Park you like one type of music: pop. Just because those three artists present their pop in different formats doesn't change what it is. If you also happen to like Miranda Lambert, that doesn't make you a country music fan that makes you a Miranda Lambert fan.
Think about this: When did the term Indy rock become the definition of a musical sound and not music that was written, recorded, and distributed on a shoe-string budget by a tiny record label with no connection to the big music labels? Answer: the minute record execs discovered that some people will go out of their way to listen to obscure, poorly-played music just so they can feel unique. Speaking of unique, where did this idea come from that just because an artist doesn't sound like anyone else makes them exceptional musicians? I don't care if you're fusing afrobeat and delta blues with crust punk if it sounds like you're playing three styles of music poorly at the same time. Then there is Lady Gaga different or as I call it marketing different. Here is a woman who sounds EXACTLY like 80's Madonna with a splash of R&B, but somehow gets lauded as being the most original artist since the dawn of man because she wears odd outfits. But I digress...
Who cares, right? Why does it matter if someone is into one specific style of music or 36? It matters because it is indicative of the state of the American psyche. Everyone wants to fit in despite all of the stories we've been told of this country being the one place in the world where you're free to be an individual. No one is going to come to your home and arrest you for banging out to some Blut Aus Nord if you so choose, but the social consequences can be interesting. I often get curious glances when I tell someone that I listen to a lot of hip hop and also a lot of metal (death, black, sludge, and doom being my favorite styles). People often assume they can tell what kind of person I am solely by my musical choices. That is the very reason why everyone you meet tells you they listen to "everything"; they are afraid of being reduced to a single line definition of their existence (this happens a lot more with clothing, but that is a different post altogether).
There are people out there who do listen to a wide variety of music. Some people can go from Celine Dion to Aesop Rock to Brooks & Dunn to Agalloch and not think anything of it. I'm not one of those people and, most likely, neither are you. Our fear of being judged for saying anything out of the ordinary, even about something as trivial as music choices, goes further than most people would like to consider. The same mentality that got the American public to at one time support a war against a country with no connection to 9/11 (remember 2003? It wasn't that long ago...) in two terms as president likely comes frome the same place that makes you think people listen to Arcade Fire solely because they like the music.