I keep wondering this myself. I've never used one because I just don't get the appeal. I assumed people used it because it was cheap, and I didn't mind paying more for a hotel...but then saw it's even more expensive than a hotel!
Hotels pamper you, clean your room and towels daily, often have food and alcohol, often have shuttles to take you around, great locations, etc. AirBNB has none of that. I have to be missing something?