I don't get the idea of 15 more practices thing. I never did. Usually at the end of the year, the starters are looking to heal up injuries and not go full out and practice more. Sure, they would love to enjoy a trip to California or Florida, play a game with smiles.
But also, many bowl games are not as viewed as how important the game used to be. Since McCaffery skipped his bowl game with Stanford to get ready for the NFL draft, tons of players have done the same thing since (and to avoid injuries). It's really gotten bad the last 2 years. Remember when KSU was to play Alabama, and several players from the Tide chose not to play? Alabama still rolled over KSU.
It really stinks when you get a matchup the looks fun on paper, and the QB for the other team chooses not to play, and their RB and 3 best players on defense.
The extra Husker practices from Bowl games is just some extra conditioning for the healthy Husker players, and gives the staff something to do (and Nebraska writers something to write about). For the fans it's another game to look forward to and another reason to drink in mid December lol. I'm joking, I'm kidding... but there is a little truth in that.