Over the decades, Pitt and Penn State have had different primary rivals. Way back when, Penn State and Penn played annually, and that was a big game for both. Incidentally, most of those games were played in Philadelphia (as most Pitt games were in Pittsburgh). As Penn faded into the ivy, Syracuse filled the spot. Meanwhile, Pitt had rivalries with Westminster, Duquesne, Carnegie Tech and W&J -- all which dissolved in time. Reading old newspapers, I get the sense that Pitt considered Notre Dame more of a rival than anybody else for many years.
Pitt got Joe Paterno's attention when John Majors arrived in Oakland in 1973 and Pitt proved it was no longer a patsy. From 1973 till the end of the original run in 1992, Joe Paterno treated Pitt as Penn State's chief rival. His gamesmanship, his sanctimonious posturing, his whole schtick was the stuff of true rivalry. Paterno once said he would rather beat Pitt than go to a bowl game. Yes, Penn State won most of those games, too, and every one of them meant a lot to the old coach.
Once Paterno got PSU into the Big Ten, he didn't need Pitt any more, and whether out of spite or whatever he shut down the series after the revival from 1997-2000.
Mr Uptight Jimmy Franklin is missing out on a good thing. Here's the one school and fan base that hates his preening, smarmy guts, and he gives them the back of his hand. He'll never get this emotion from Ohio State or Michigan who will always look at Penn State as a Big Ten interloper. Like Rutgers.
