Boise State and UNLV were given strong consideration to make the NIT tournament this year since each team had over 20 wins, but with 13 automatic bids handed out both the Rebels and Broncos were passed over for other, more deserving teams.
The 13 auto-bids is a result of a fairly new rule where a regular season conference champion receives an automatic bid if they fail to qualify for the NCAA tournament. So, 13 of the 32 spots were already taken leaving just 19 at-large spots.
Just for fun here is the NIT bracket:
With the NIT passing on both UNLV and Boise State, the two schools are not going to be going to any post season tournament. The CBI and CIT more than likely extended a bid to each school, but those tournaments actually cost money to host and/or attend each school turned down those invitations.
For Boise State, not making any post season appearance has to be disappointing since they returned all five starters from last year's NCAA tournament team, and they vastly underachieved.
UNLV is always considered a threat to make the NCAA tournament but the loss of Anthony Bennett to the NBA, the unexpected transfer of Mike Moser and graduation put a damper on this year's teams post season chances.