Atrios says that all policy (and by extension, all policy debate) is tax policy, and I think that's about right.
Consider the policies of Dubya. He gave a hundreds-of-billions tax cut, then launched two wars, and put them on the credit card. So he had a definite tax policy, namely, "Somebody else can worry about this."
That and the consequences of the financial crash that sploded the economy during the last year of the Dick 'n' Dubya debacle pretty much sets us up for the present.
In most countries that have progressive income taxes, the policy objective is income re-distribution. This is accomplished both directly, by taxing the well-off at higher rates than the less well-off, and indirectly, by using tax revenue to support social programs, primarily a state pension and a medical treatment system financed by some sort of government scheme.
That's the promised land, and we'll get there after 40 years wandering in the wilderness. By my reckoning, we've got about seven years to go.