Thing is, we keep finding out again and again that having a very broad training mix in the baseline model makes it better across the board, including in those specialized tasks when you fine-tune it.

As I understand it, the general ability to reason is what the models get out of "being trained on the tax policies of the Chang Dynasty", and we haven't really figured out a better way to do so than to throw most everything at them. And even if all you do is make toast, you still need some intelligence.