As an invention of progressivism the income tax eventually worked a revolution in government by allowing government to grow to gargantuan size with a ready pool of available cash, stolen by force from the population's income. And it is no coincidence that the first major expenditure financed by the income tax was US entry into The Great War. Not long after which came The Great Depression. If progressive ideas were good ones, no one seems to have paid much heed to the early evidence to the contrary.
Every effort by the people since the introduction of the income tax to obtain deductions, exemptions, credits and other incentives in the tax code should be understood by conservatives as wholesome reactionary, counter-revolutionary, rear-guard opposition to what the income tax represents, but today you can hardly find a conservative who will even entertain the idea of overthrowing the income tax, let alone any other of the so-called "achievements" of the progressive era. In fact, some so-called conservatives have become veritable cheerleaders for the income tax. Rush Limbaugh, for one, can't seem even to imagine an America without one for the first 137 years of its existence. An originalist in name only is he.
The problem with so-called Reagan conservatism, then and now, is that it makes peace with the tax code, just as it does with the social welfare state, including Social Security and especially Medicare. Mitt Romney and Paul Ryan actually campaign on just such a platform of preserving Medicare for future generations. As Reagan compromised in the direction of liberalism in the 1986 tax reform, so will they.