Because I remember a great deal of interest in college players like Herschel Walker, Marcus Allen, Billy Sims, George Rodgers, Archie Griffin, and Tony Dorsett in the mid 70s to early 80s when I was a kid. I still remember a lot of the coaches-Bear, Woody, Bo, Johnny Majors, John McKay, Don James, Tom Osborne, Joe Paterno, Lou Holtz, Vince Dooley, Bowden, Jackie Sherrill, Schnellenberger, Darrell Royal...

Other than the Chargers, Vikings, and Colts, I don't remember a lot of pass first NFL teams with wide open offenses from that era.