Due to how one is raised, he will come to different conclusions on what is moral and immoral.
Much like -
Due to what one has listened to in the past, he will come to different conclusions on what is worth listening to and what is not.
For example when I found this site, I found it because of Dream Theater and Yes. Why did I listen to Yes and Dream Theater? I grew up with these bands and will always like them. Dream Theater reminded me of 80's bands like Metallica, Van Halen, and so on. Why did I listen to Yes? It just runs in the family and I've heard them around most my life. So what attracted me at this website and in the prog-genre? Bands that sounded similar (not clones) to Dream Theater and Yes, and from those similar bands, I find even less similar bands and so on and so forth. It's a chain of acceptance from one band to the next due to what we already like and what we're used to thus far.
How can you just pick one band or one sub-genre? It's obviously going to be slightly different for every single person. It's psychology!