I remember the sheer awe when I first learned there was a huge open web outside of AOL. I'm sure people nowadays are aware of the rest of the web, but if the draw is minimal, they will likely get stuck in the same loops of well-trodden space.
A lot of the same people who kept that AOL walled garden alive, just migrated to Facebook. To them Facebook is the web, the restaurants they like are there, the tired celebs they worship are there and whatever crazed conspiracy theories someone told them at work or at church are under Facebook News. It's comfortable and I agree with you and like how you phrased it as "the same loops of well-trodden space."
I dont think they re worried much about that anymore , people always return, they ve established their position. OTOH, it would be nice for google to have some serious competition on the web, esp. considering that FB has a great NLP AI team.