Re: political power
The tax system is one of the main methods used by politicians to reward donors and friends, and punish political enemies. This has been true for decades, and true for all political parties.
Every gimmick you see in the tax code is part of this. Lobbyists, political activists, and many others spend a lot of time in Washington (and state capitals) trying to get "tax breaks" for themselves, and "penalties" for their enemies and/or competitors.
This is also why "targeted" tax cuts are so much more popular with politicians than "across-the-board" tax cuts. Targeted cuts give one political power.