If your friends are telling you to listen to these songs because they heard it from someone else, that's exactly how things catch on.

People may like a particular piece of music, but then the additional testimonial that goes along with it from others can do a lot to help that decision.

I think the best answer to that is that they just aren't sure. Part of the equation is what other people think about a song or a product. We live in a social world where if we were the only person who liked a particular song, and no one else liked it, we ourselves might not like that song too long, either. Other people don't accept it, and that puts pressure on us to try and fit in.