I also don't see a problem with giving they top 16 teams a "bye".
Seems to mean doing well in your games matters. It also means the teams "on the bubble" playing for something in early March are at least mid, and not bad teams with a big enough fan base to be in a good conference. It also means the small conference tournaments mean something.
Just putting in the best 68 lessens the reward for being great, makes the bubble teams inarguably worse, and the small conference tournaments would be meaningless.
All in the name of "not discouraging good scheduling." I have yet to see any evidence of teams doing that. And the "good" games aren't actually good, they are meaningless exhibitions between teams comfortably in the tournament.
If we were constantly getting 13 seeds winning the national championship, if just getting in meant you had a chance of winning, then sure, put the most talented 68 in. But they aren't. So why would we want to worsen the product, make the regular season even less meaningful just to make sure USC (who would be comfortably in) would get like a 25th chance to reprove how mediocre they are?