Costanza
I'm out there, baby!!!
Can of worms.
There are calls that are black and white (was the guy out of bounds or not?) and then there are "gray area" calls like PI. If you allow review of PI calls, you have to also make it OK to review holding calls, personal foul calls, etc-etc. Plus the NFL doesn't want to take any power or legitimacy away from their officiating crews or put them in those situations.
No way in hell is a PI a gray area. Nor is personal foul. Holding, yes. If the holding has nothing to do with the play, let it go man.
And your last sentence sounds pretty spot on.