The difference is in the accessibility.
If a team like Utah went undefeated (not that I think they will) they'd win their conference and almost certainly be in the playoff.
If BYU went undefeated with last year's schedule (pre CCU addition), they'd be in the Boca Raton bowl.
If BYU went undefeated with this year's schedule, they'd be in the NY6.
If Utah State went undefeated, they'd be ranked 16 and playing in some no-name bowl.