Tax codes are a great example of something changing frequently, and something very nuanced. So, the training data doesnt exist for a future year's return while are rules are already changed.

So, instead of math/programming, tax codes approximate the real world better. Whereas math/programming/images/languages are frozen in time. I find this fascinating. Almost like the legal system, wherein rules are laid out in english but are almost mathematical in the sense that there is a legal/illegal judgement made for almost every action, but that judgement is not easily determined.