I used to think the same thing but it's not really a scam. It's a way to allow low income people to pay less to the government in taxes because they have less to give.
When you move things over to sales tax, high income folks don't end up paying as much as they could because they don't spend the money as aggressively, and low income folks can't afford the bare minimum so you have to either further subsidize them (so you took their money to give back to them?) or deal with the ensuing homeless problem/never ending poverty cycle.