You mean other than the fact that Boise State won their last BCS bowl?
BSU and TCU may be every bit as good as you say, they just don’t go out and prove it every week.
In 2006, BSU beat Big XII champion Oklahoma
This season, BSU beat probable ACC champion Virginia Tech
http://bleacherreport.com/articles/501788-boise-state-football-why-does-most-of-the-country-want-to-see-the-broncos-fail
"I've said this before and I'll say it again, put money aside, call up the best schools in the country, and get the games done. But here's the problem with that line of thinking. The likes of Ohio State, Oklahoma, Texas, Alabama, Auburn, Florida and every BCS team that isn't in the Pac-10 won't schedule Boise State."
"Why? Because they'd rather pay San Jose State, the worst the WAC has to offer, a hefty sum of money for an easy win than pay any amount to bring Boise State in for a real challenge."