Did you know that the income tax was introduced during the CIVIL WAR (1861-1865) to help pay for it?
The income tax has probably stuck around so long partly because there have been and still are people in government who still cling on to the hope that we will someday redistribute all wealth in the nation and that the Income Tax is one way to accomplish it.
Tax laws in this country have been used by the government as a means to accomplish social engineering of one sort or another. For instance....married people get tax breaks (to encourage marriage), people with dependents (mostly children) are given tax breaks (to encourage having children?), donations to charities are tax exempt (to encourage charitable giving), interest on mortgages on first homes are tax exempt (to encourage home ownership), IRA and 401(k) contributions are tax exempt up to a point (to encourage savings on retirement). Perhaps such things should not be part of the government's mandate. A national sales tax might help to avoid a lot of this.
And if there were a national sales tax, what should its rate be set at? 25%? 33%? What would the effects of a national sales tax have? Would people have more money to spend? Probably not, since the sales tax would probably be revenue neutral. Would it encourage savings and investment? Very likely, since such activities would very likely be exempt from taxation. Of course, charitable giving would be free from taxation by definition, since you aren't purchasing anything when you give to a charity.