Why not just have one payment system to rule them all run by the government that is required by law for all payment of employee-driven services? Businesses cou

Why not just have one payment system to rule them all run by the government that is required by law for all payment of employee-driven services? Businesses could save a TON of money on payroll systems and HR. A government-run system--presumably--would take care of withholding the correct amount of taxes and also making sure the business/person paying a salary never has to worry about running afoul of the law (having the IRS or equivalent) come after them.