Because gov't is just not big enough yet.
I vote straight GOP every election (although I will abandon the Republican party if they sell out our nation's military to Sequester). If it were my call, we cut all tax rates, we have a consumption tax that hits everyone fairly, we eliminate the estate (death) taxes, we eliminate the give away Earned Income Tax Credit fat refund of bills to those who pay no Federal Income Taxes (this is simply a welfare program), and we scrap ObamaCare.
But, I am not King. So, there will have to be some GOP proposal to tax energy profits or eliminates mortgage deductions for vacation homes or mortgages above $1 million. Otherwise, the Democrats won't accept any give away entitlement reforms.
Because gov't is just not big enough yet.
or - because you peasants still have way too much money left over after all the taxes we've been extorting from you already. You all just ain't paying enough taxes (don't you know).