To everyone out there, don't be deceived when you read about the marginal tax rates, since no one ever seems to talk about the "hidden tax"- before you EVER get to the graduated "income" taxes, you also pay- off the top, no deductions, 15.3% payroll taxes for Social Security (FICA) and Medicare (you may only see the 7.65% that is shown on your paycheck, but since your employer has to pay the same amount besides, it's really 15.3% of your income). So if you are in the 31% tax bracket, you're really paying 46.3%- before you ever get to any state income taxes you may have to pay, or gas taxes, or sales taxes, or excise taxes, or tolls or user fees.
A flat tax would be simple, straightforward, easily-administered, [relatively] fair... so you're right, it will never happen. Legislators would be struck dumb by the prospect of not being able to use tax policy to attempt to regulate behavior of which they do not approve.
PS- come on over to Dallas one of these weekends and help me work on the brakes on the Caddy (I almost plowed into a rice-burner at an intersection last week!)... and the A/C (have you priced R-12 lately? Ouch!); and I need to put a new convertible top on it - that's some work! Owning these big ol' beasts is a responsibility, sure enough.
As you are in the UK (right?) you may not be aware of one fundamental principle here- the federal government is not the dominant provider of services here in the US (or, is not supposed to be). In our system of government, under the Constitution, the states are supposed to be dominant, with Washington providing the things that it is uniquely capable of providing (like protection of constitutional freedoms, delivering the mail, defense of the national borders, protection of interstate commerce rights). Thus, denying the federal govenment much of the money which it now collects doesn't mean government cannot spend money on common good things like education, etc.; rather, it means that the taxing for such programs (and the decisions regarding implementation of such programs) can be doen at the state or local level, where (by the way) the elected representatives are more likely to be (1) knowledgeable about; and (2) responsive to; the needs of their constituents.
The federal government has used its ability to tax and spend with substantial effect, resulting in the growth of government as an industry (as opposed to being a service to the people and to the states). Unfortunately, the further-removed government is from the people (eg, federal vs. state, county, city or precinct), the less-efficient or responsive it tends to be in the dischrage of its duties.
Now, I have to go and discharge some of my duties as a parent. I am the weakest link. G'bye.
...three miles from BRONS, clear for the ILS one five approach...