As someone who loves the ACC and can't get enough basketball in March I've watched the NIT quite a bit over the years. What I've found is that it's one of the toughest things to predict--ever. We assume teams like Florida State and Cuse will have something to prove, and will also be the best teams, but all too often those teams lose in round one.
NIT matchups also seem purely made for TV. Watch Clemson and Michigan play in 1st round or something random like that, while 2 teams you never heard of play each other.
Bottom line is I think many of the major conference teams who had a shot at the 64 (and who we think might do well) just aren't motivated enough, and rarely move on...