Pretty much for the same reason why there's both normal and dungeon carving versions of dungeons. Some people prefer the new way, and some people still don't know how to make it work.
EDIT: Whoah, when did you post, Sephiroth? :p ... Well that's what you get when you're easily distracted, Shads....bah... The paragraph above works well enough.
On that note, I'm still trying to figure out what to do about caves in terms of dungeon carving mode. There are naturally two height variation levels in there. May as well stick with the upper one if I'm going to make one.
