William H Macy probably doesnt monitor how his wife spends her money, and he wouldn't want to, because much of the time it would things like clothing herself, Starbucks, maybe the car she drives, things she does with her girl friends, lots of "noise", so her having spent $15k on a college bribe could have gone under the radar.

Then again, maybe he knew, but there is no paper trail linking him to it, thus no criminal charge.