A sales tax also makes merchants tax collectors which I consider immoral.
Flat tax still does not have all citizens skin in the game...a sales tax would (and the mechanism is already in place in most States [45/50 IIRC]). Plus, as it’s a line item on the bill, it’s easy to see what gov’t is costing and requires NO collectors (IRS); biz remits to State, State remit to Fed
I have the same feeling about employers being tax collectors; let alone ‘H.C. providers’.