The answer is "Green Light". Link.

So they disable Linux overclocking and punish card OEMs to not implement any overclocking by any mean, exactly to have less chip failures in desktop area(and less RMAs/replacementS), so they can sell those chips MUCH more profitable in Quadro/Tesla area, instead of desktop (giveaway).

What backs up this claim, is the fact that coolbits disappeared exactly for Fermi and Kepler chips, exactly when this program was initiated.