It might have been half full because of the following:
1. Both Teams Stink
2. Fans could stay home and watch the game on NFL Network
3. It is Thursday night and a lot of fans have to get up
and go to work on Friday.
For the price of tickets for a family of 4, concessions, and parking you can buy a 60" tv at Walmart and watch it at home. Even NFL Network games are broadcast locally.