The power dynamic between the gifter and the giftee isn't that simple. Even bribes dynamics will change a lot depending on who does it and to which amount.

There is a whole antropologic field around that, but to keep it short, if you pay your palace and all expenses with the money funneled to you as gifts, you're not the one in control.

Fun read: https://en.wikipedia.org/wiki/Gift_economy

How feeble they might be in today's political arena, optics are still important.