I would bet that there are more non-contact injuries than "hip drop" injuries. I can't count the times I have seen someone get a season-ending knee injury from cutting and even a few from celebrating.
All these crap rules are for is more NFL control of winners and losers.
Cut blocking can be hazardous to knees for sure, but I would argue that cut blocking happens a lot more frequently than hip drop tackles, making hip drop tackles more hazardous per event than cut blocking.