Many employers believe it's unnecessary to reward employees for a job they are getting paid to do, but what employers need to understand is that materialistic reward systems are not at all the same as recognizing employees ...
This is exactly what I talk about in my speaker program on Employee Motivation and Engagement. You must praise people when the do an exceptional job - when they knock the ball out of the ballpark. Yet, praise - recognition for doing an exception job above and beyond the call of duty - is frequently not mentioned, paraded in front of peers, or given an appropriate round of applause.
And that's a complete turn-off to your best performers. They'll start leaving over time when required praise is not given.