NFL has to rework how it grades, evaluates and rewards refs

My guess is, that they are graded more harshly for missing calls than they are for making calls that should have been left uncalled.

Instead, making unnecessary calls should be one of the worst things you can do as a ref, possibly second only to failing to call penalties that can or do result in an injury.

If you demote or fire the officials who get flag happy, you eventually reduce the number of flags.

Its a management issue. You get more of what you reward and less of what you punish.