[bluGill]

Everybody is in favor of simplification until it eliminates the complex part that benefits them. Eliminating the mortgage interest deduction harms a lot of people because their taxes go up significantly. (the latest tax reform pushed the standard deduction high enough that most people don't gain anything by deducting their interest - maybe in a few years nobody will care anymore and this can be eliminated)

People want simplified taxes, but they write letters and vote when their taxes go up, so more complex taxes are rewarded despite that want.