Not most. There are some that are having issues filling their seats...usually the teams that have sucked for a few years. Good teams are still filling their stadiums. The 49ers have been bad since management mucked up the Harbaugh deal and fans are sticking it to management right now. However, Lynch looks to have gotten some of their personnel issues figured out right now. That game was a fun one to watch last night.
Look at the AAC teams- Temple, plays in an NFL stadium not close to campus. USF-plays in an NFL stadium not terribly close to campus. UCONN- sucks (in football, still a relatively new D1 program), Navy- usually a full stadium (on campus), ECU- on campus, one of the best fan bases in AAC, UCF- hit or miss and fans are fickle and fair weather, Memphis-plays in a giant stadium, not on campus, but usually good crowds. Houston- on campus and usually good crowds (but also somewhat fair weather), SMU and Tulsa have the same issue in that they have a relatively small private alumni base who don't always stay in the metro Dallas or Tulsa areas after they graduate. Tulane- years of awfulness combined with not having an on campus arena. Also, similar issue with TU/SMU.