Lets see, 8 games are required to be in conference. So that leaves only 4 games left.
Some schools are required (especially the public university) to play the in-state team from another college. ie. Georgia-Ga Tech, Florida-Fl. State, etc...
A tune up game against a minor in-state school is a nicety, as it brings in revenue to both teams.
Don't forget traditional rivalries.
There are only so many games to schedule.
btw, why doesn't Ohio State try to schedule these games against the SEC schools during the regular season. And the regular season games would be in September-early November weather. Not exactly arctic weather at that time.
And who they play during the year has nothing to do with Ohio St. getting their asses handed to them the last couple of years.
p.s., Georgia played Oklahoma St. in it's opening this year, and they play Arizona St. next year, those are outside of the Southeast.
Auburn opened this year against Kansas St.
I'm sure there are others, but so far I killed that excuse for losing.