Samsung put 4 Cameras on Galaxy A9

You seem to forget the fact that most people aren't photographers by hobby, they just want to snap a pretty picture that may pop up. Then the camera is a waste of money. Hauling a phone is not difficult, but hauling your camera with seventy lenses around is not exactly practical for everyday use.

Why would the owner of a $1k piece of garbage need more than one lens

He doesn't.

Then get an integrated camera with an optical zoom.

But he doesn't need that either. The average owner just wants something that takes good photos (to the untrained eye). Not something that requires training (all that ISO/shutter speed/etc. shit) or knowledge.

that's quite a lot of cameras for one phone.