I literally came here just to ask about this.. I just bought a huge block of pecorino romano (I make cacio e pepe with it, delicious if you want to try a new/simple recipe). Is this common to put on pies? It has a great taste, I just never thought about using it on a pie.
Elohel, while it is very traditional for New York area pizzerias to have a jar of cheap grated cheese on the counter, I would say that the number of places that put hard grated cheese on the pizza could be a minority. It's much more pervasive in New Haven.
One thing to keep in mind, and you might find different opinions on this, is that the places that do use Romano may not use a high-end version. Freshly grated Locatelli, depending upon how much you use, can get pretty overpowering. Pre-grated might lose enough of it's intensity to be used in larger quantities, but based upon my knowledge of how cheap pizzeria owners generally are, I have a strong feeling that they're using a lower grade– not Kraft, but not Locatelli either.
As far as using grated cheese in general, it's something I do occasionally, but, for a well melted/bubbled, high fat, buttery tasting wholesale cheese, grated cheese shouldn't be mandatory.