I think that is a big problem as well. Government shouldn't be using taxes to pick winners and losers (not a popular opinion I know). Another issue is when we talk about making the tax code simple is we overlook all the taxes and just focus say on income tax. There are so many other taxes (and the always classic it isn't a tax but a "FEES") imposed by the both the federal and state level that the true impact of taxes to the individual is hidden by design. For example Trying to figure out your tax burden if you move states isn't simple. Sure income tax is lower here, but higher property tax and sales tax, and other dozens of fees.
For states I have always wondered why can't we simple get rid of all taxes, fees, etc, and deductions and credits. A state simply says here % of your money we will collect each year. Then it is easier to compare moving to FL vs. CA vs. MA, etc.
And the answer of course is simple. A complex tax system allows being able to tax people more and allows buying of votes.