Taxes. Until WW2, taxes were not something the majority of people had to pay. It was pushed as a temporary tax (the Victory tax) to help fund the war, with promises it would end with the war. Not only did it not go away, it has been used quite extensively to comb through a persons financial transactions. Never mind the illusion of the fifth amendment, it does not apply to any financial transaction (incoming or outgoing).

100% this.