There is only so much time to practice per week and clearly Frank spends much of it on defense and rebounding. I'm sure plenty is on offense, but he's not going to throw out some motion offense. To be kind, I'm sure Frank would listen out of respect to Knight, maybe even implement a wrinkle or two, but Frank has a system and it works just fine.
Just look at the offensive efficiency of his teams. I mean we threw out Kent, Colon, and a young Jam-Sam in the paint last year and he still finished in the upper 1/5 of college basketball in offensive efficiency. There is more to offensive basketball than offense.