Because teachers love their students. The school says the budget is coming up short and there won't be enough crayons to go around, so the teacher has the choice of telling the students that there is no more crayons or just buying a bunch of crayons themself. But applied to all supplies.
Oh boy when you find out about all the "edu-tech" companies that have sprouted up, creating "solutions" to non existent "problems". A lot of them also have family/friend relations to local governments :)
Is it too much to ask to first spend money on teachers and basic supplies, and only if money is left over after that, spend it on extras, new tech, experiments, and administration?