The Obama Administration has been adamant about raising tax revenue by raising marginal rates rather than by closing loopholes and capping deductions, even though the latter solution would raise as much revenue as the former. Why all the insistence on rates?
Loopholes in the tax code have historically been used to manage behavior, as well as to reward and punish those who are in or out of favor with the powers that be. If President Obama gets his way, he will still be able to use loopholes to reward his wealthy contributors, while also using the tax code to punish those who oppose his policies.
A flatter, fairer tax code with few deductions and loopholes would mean that those donors who favored the President with their millions, would have to pay like everyone else.
It is not about the revenue, it IS about the power.