The reason it's so byzantine because taxation is control. The government wants to control your behavior, and when it's prohibited by law from doing it by threat of violence or coercion, it still can do it by employing the tax code. What happens if the court finds the government can't force people to buy health insurance? We declare it a tax on not-buying health insurance. What happens if the government wants to ban something, but is concerned the courts would find it overstepping its boundaries? Tax it until nobody can afford it. Want people to do something? Declare tax credit for it. Want to subsidize certain company? Issue them tax credits. Etc. etc. Nobody would be willing to give up such a versatile tool.