If I give money for an endowment that supports future replacement of electron microscopes, that does fuck all for your tuition.
Presuming of course that they absolutely weren’t going to replace those microscopes without that endowment. If they were, then that endowment frees up some money elsewhere in the budget. Unless literally every penny they hold has strings attached, then the fungibility of money means they could use general fund money they aren’t spending on X because of an endowment on Y instead.