Let's boil it down to a few facts that work against Pitt.
1) Pittsburgh is a medium sized market now. LA can absorb multiple NFL teams and say support an USC and UCLA. NY has two pro teams and really could care less about college football. Miami is a large market can support pro and college.
2) On that note, the Steelers have been the most successful franchise since the AFL/NFL merger. Championships, Conference Championships, Division Championships and I think the best overrall record. Since 1970? Pitt is has had 8 really good, nationally relevant seasons. The Dolphins in contrast, haven't been relevant since Marino played, which helps programs like "the U" gain traction with the locals. Here? NFL success far outstrips college success.
3) As I (and others) have mentioned many of times, draw a 250 mile circle around Pittsburgh. You hit Penn State, Ohio State, WVU, Maryland, Michigan, Notre Dame fanbases. 4 of those fanbases are among the largest in the sport. Contrast this with Minneapolis, a much larger market than Pittsburgh, you just touch the Wisconsin and Iowa fanbases. Outside of Georgia Tech, no other schools face such proximate college football fan competition. Plus Atlanta is much larger than Pittsburgh and the Falcons are nowhere near as popular as the Steelers. It is hard to grow with the casual fan here.
4) and a PSU/WVU/Big 10 centric local sports media (also pro centric) do not give Pitt much of a thought. So there is no hometown media to act as cheerleaders and help create interest and sell excitement for the program. Hell, to the contrary, even when we do have something good, we have media detractors diminishing it, outright despising it, or ignoring it.
That's just too big of a mountain to overcome if there is ever that super division of college football for Pitt to participate in IMO.