@Mashburns I don't want to speak with 100% certainty= just what I've been taught (or at least what I can remember), what I've inferred from experience as a coordinator and head coach at both 7A, 4A, 1A, and been told.
1 reason: They are not allowed to if the money is donated through kids (i.e. fundraiser, donations in the name of jimmy, etc). The reason being- that money is by kids and for kids. It should be well noted that most booster money comes from student fundraising and checks written on behalf of jimmy and his two little brothers. Money not raised from kids by redbook definition, could essentially go to a coaching staff- so long as the bilaws has provisions on how bonuses and payments are dispersed (or at least a calendar).
2 reason: They are not allowed to due to lack of a proficient finance operator within the booster. The Booster (if trying to allocate funds to a staff) would need to have seperate accounts for student raised money and 'random' donations. These random donations could be alumni, endowments, company sponsorships, etc etc. Too often all of the money goes into one account and the financial books are not established well enough to note the difference in what is raised by kids and donated without limits. Treasurers usually don't make copies, don't actually run a finance book, and only do audits when they are scared or a massive booster turnover.
3 reason: Most booster clubs, within bilaws, do not have a clause saying that a paying/active member cannot be part of the school board. The reason this is so important is because teachers cannot accept payments from within the school system that is not noted on pay stub. This is where things get sticky and a lot of my confusion starts. Small details such as where the meetings are held, meeting minutes, exact language, etc. All of these things cost money (i.e. lawyers for review), that most boosters aren't willing to pay due to the amount that the coach/kids would lose.
4 reason: Lack of audits. Pretty simple, most boosters try and skate by. That just doesn't cut it and rarely have the ability to approve certain allotment.
Hope this clarifies some of my points, I also hope someone else with more experience can chime in.