(This occured to me the other day as I looked over my Rdio dashboard.)
Human musical tastes evolve much like our culinary tastes. When we're young our tastes have not yet matured physically or mentally and we tend to enjoy extremes of experience (the sweeter or louder the better). As we mature, so do our tastes, and we begin to appreciate subtlety while becoming increasingly turned off by more intense experiences. Finally, as we grow truly old, we just enjoy anything familiar that doesn't make us sick.