Because musical tastes evolve. It has nothing to do with being more "civil", many of the lyrics in rap (especially gangsta rap) are just as (if not more) vulgar than the types of lyrics you heard (and still hear) in rock/metal.
Personally, I've been a fan of alternative rock (e.g. The White Stripes, The Raconteurs, The Black Keys, etc) for as long as I can remember, and I'll likely stay that way forever.