Blue chip programs get the benefit of the doubt in rankings (especially pre-season and early season rankings).
They help people outside the conference's footprint associate something tangible with the conference (I say ACC, people think "Clemson;" I say SEC, people think "Alabama/LSU").
They pull/push the rest of the conference to be better (think Gonzaga in basketball).
Their year-over-year success gives the conference opportunities that would otherwise be withheld (Wake Forest got no respect this year as a team that was undefeated at the mid-season point; if Clemson had the same record against the same teams, they would have been top-2 and in the hunt for the CFP).
We can talk about "parity" all we want, but we've recently seen the Pac-12 have years when they were VERY competitive against other conferences - and perception was still poor because USC and Oregon were down.