I'm not sure whose schedule you were looking at over "the past decade or so" but it wasn't ours. We've played many more teams than "Tulsa and directional schools." Going back to 2009, we've played the following P5 teams in non-conference:
Oregon State
Pitt (2x)
Florida State
Mississippi State
Arizona (2x)
Washington State (2x)
Georgia
We've also played a home-and-home with Boise State, which I don't see a lot of P5 teams lining up to do.
Are those all of the greatest teams in the world? No, but it's hardly "a bunch of directional schools and Tulsa"... we've generally had one P5 (or a pseudo P5 like Boise) on the schedule every year for the past decade or so.
Over the next decade-plus, we finish our home-and-home with Arizona State next year and then have home-and-home series already set up with Arkansas (2x), Oregon, Alabama, Colorado and Nebraska. (Yes the latter two suck now but they may have their shit together when we finally play them).
Why should we punish ourselves by putting another really good P5 school like OU on the schedule in any of those years, essentially giving ourselves an 11-game conference schedule? That would just be fucking stupid, even in the expanded playoff era.