I imagine Disney passed on the idea of a rooftop restaurant at PIT because they had an existing example in the California Grill and found it undesirable.
California Grill is a hassle for management and employees, there is always someone there trying to watch fireworks for free or minimum cost and begging "aww cmon". Prix fix is obviously meant to help address that, and profitability, but I'd doubt it prints much money. Moneybags Bob will pass on another restaurant like that. He'd rather put ostentatious DVC on top, that's how they print money, and again they know just how much they'll rake in because they have an example in the bungalows.
I actually think a rooftop restaurant would work better if they just let anyone watch from up there for free whether they paid for anything or not. By fighting the horde they keep the deck protected for the few that make it causing it to be sought after. If it were always crowded it would be less desirable, no longer a "best kept secret" heavily publicized by vloggers and tour guides which is ironically not a secret. Fire code probably prevents allowing crowds on that deck though.