This American Life's "Gossip" episode had a story from someone working on a reality TV show. TL;DR Everything is staged and drama is fabricated if it doesn't exist.
I don't doubt that you're correct overall that everything on "reality" shows is staged: my neighbor was on a dating reality show on national tv and lots of it was fake. Just for the record, though, as a huge fan of TAL, their site describes that story as based on a work of fiction.
http://www.thisamericanlife.org/radio-archives/episode/444/g...