They are famous for being famous. I think there was some sex tape or other scandal that started it. Unfortunately, we live in a time when such people can live of this pseudo-fame through their own reality TV shows and other weird endorsements.
Because people pay attention... the Kardashian's attention tactics are working... hats off to their business skills...
The public has an unwavering devotion for celebrities, some do wish well, however most people watch to see when they crash and burn. Don't worry, we will all forget about them soon enough, or one of them will fly off the handle
It all started with Kim's sex tape, I'd imagine. They're an entertaining family and that's fun to witness. The worst/most unintelligent argument against them is that they don't deserve to be famous or that they're all idiots - which is ridiculous. They managed to build an entire business empire out of their name from almost nothing, which is beyond admirable.