Let's not forget one significant driver of complex tax code: the IRS almost always has dirt on people with pretty one-side results when they come after you. Rather than speculation, a number of ex-IRS auditors made this claim. The idea was that they have a limited amount of resources to find tax cheats and it's hard to prove on some of them. So, they first make the tax laws favor them by creating lots of uncertainty which already appears for other reasons. Then, they hit hard in terrifying ways when they come after people with little resources to fight back: huge fine, people kicking in their doors, seizures of property, etc. One agent wrote that the goal was a form of terrorism where the few hits they made would scare others into compliance despite the fact they didn't have resources to get to them all.

So, it won't get simpler. It benefits IRS's strategy and many stakeholders using exemptions, too.