Most OU fans would kill to fill seats the way UNC, Duke and KU have done for years. But according to an article I read two years ago (it was posted here back then, just don't ask me to find it), even the so-called elite basketball schools don't fill up their arenas for every game anymore. The article cited a down economy, gas prices and a number of other reasons for it in the last few years.
In the case of Duke, a full house in Cameron Indoor is 9,314 fans, unless they make room for people who don't mind standing the entire game, and I'm sure even that space is limited. By contrast, seating capacity in the LNC is around 12,000.
Average attendance for home games in the LNC last season was 10,650. Keep in mind, that was when we had a 13-18 season. Two years ago when Blake led the team to an Elite Eight finish, the average attendance at home games was 11,490. Our average attendance this season is down to just over 8,100 so far. It may pick up some when OSU, UT and KU come to town.
The point is, there aren't many schools that "pack the house" for every game. And contrary to what fans of the three schools I named have claimed for years, they all have empty seats at the lesser games when ticket holders don't show up. OU does, too. It's a problem everywhere.