I believe that in any season you will have some games where the game attendance can be described as either 'soft' when the weather is bad, the opponent is bad, the timing of kick off is bad, or other major events can have an impact.
I clearly can remember during the'94 or '95 season (apex of Husker history in my opinion) on a bright, sunny, beautiful fall afternoon in October, the best team of all time played top ten ranked Kansas in Memorial Stadium. I was the owner for many seasons of a dozen season tickets. I found buyers for those not being used by family and close friends each week for years. On that particular day (there were always games where this would happen) I walked into the stadium with 4 extra tickets unsold to anyone. I tried but there were simply no takers (I made a practice of not selling for less than 50% of face value as a matter of principle I should add). There were ticket sellers all over. I specifically remember saying to my wife, I just can't understand how people would pass up the chance to come see the best of the best in this great atmosphere against a good team on a sunny calm 70 degree day
There are many games where attendance is much less than ticketed seats sold out. I would be surprised if all the seats were ever completely filled on any game even with the attendance figures exceeding seating capacity. Attendance includes every single body inside the gates (teams, coaches, press, workers, etc etc. vs seating for fans).
The bottom line is that there has always been a certainly degree of mythology about ticket demand, prices, etc. So many times one hears of scalpers getting hundreds of dollars over face price for tickets for the 'big games' but reality has always been that if you simply waited until right before kick off, you could buy tickets around face price and majority of times well below face.