Most NFL stadiums are built undersized to keep demand up as the perception is much better to have a waiting list of 20 thousand for your 65,000 seat stadium than to have empty seats in a 90,000 seat stadium. For instance, the Bills play in a stadium that seats around 74,000 and in the 90’s often times couldn’t fill it. In order to try to fill it they would black out the games locally which obviously wasn’t the greatest for local TV revenue. A full stadium always looks better on TV and will generate better revenues than a large partially empty venue.