Part of the problem isn't just # of Super Bowls, but also franchise age. The Packers, Giants, Eagles, Redskins, Bears, Lions, and Steelers have been around since the Great Depression or before. The Browns and 49ers showed up in 1944, most of the rest of them in 1959. Most teams have family lines of fans and traditions going back decades; the Seahawks are still in their second generation of fans. We're in there with the Bucs, Panthers, Jaguars, and Texans, still fighting to wedge ourselves into the national consciousness amidst generations of tradition looking at us going, "Who the hell are you?"
Like the Cowboys, a handful of Super Bowls will do it.