The big difference is that, unlike those "sharing" economy companies, Couchsurfing was not a business, and once it turned its focus to making money an exodus of "users" ensued.

Couchsurfing was not targeted at Airbnb's "get a cheap place to sleep at city X" demographic, and people that couldn't demonstrate they were looking for anything other than a low cost hotel would see their requests turned down. Couchsurfing users were willing to share their house, not for a small amount of money, but for the value of making international acquaintances (and friends for life, sometimes), which is something they also received through the service when going abroad.