I really agree with this whole Autonomy, Mastery, Purpose idea, but I also think that it misses something very important: the emotional connection to the people you work with and the company itself.

We are social creatures. A company which ensures that its employees form strong bonds will have good retention.

The other thing which is important is internal competition.

I don't have any references for these things at hand so take what I say with a pinch of salt. However, I'm fairly sure there is psychology which supports this.