An income tax taps a currently ignored source, expats (out of state workers)  The CW (conventional wisdom) of "some would pay nothing" is misleading, if they would qualify to pay nothing they pretty much earn nothing, making the argument circular.  A sales tax allows one to control tax burden to a degree by controlling spending.  The legi's would have had that in mind were there taxes, etc to make them directly accountable to the payers (US!)