Stock isn't a one-time thing.

RSUs are frequently given during annual performance reviews to employees with good reviews. For my first annual review I received a score of "Exceeds" which is second from the highest. For that, I got 35 RSUs worth roughly $19K when they vest (at current price).

In theory, good employees will continue to receive stock grants that vest over time, thus creating incentives to both stay and to perform well.