Except it ruins my immersion. Here's the thing you wanted, with no real ingame reason why you won't take it.
Actually, there's absolutely an immersion reason.
A trade simply redistributes commodities from one set of owner(s) to another one.
Mining introduces new commodities into the environment.
That is, if 50 different places each supply 100t of Gold, that's 5000t of gold in the commodity market. Trading just moves those 5000t of gold without changing how much exists (and indeed, starves the other markets of their Gold holdings).
By mining 5000t instead, there is now 10,000t of Gold in circulation, without disturbing the circulation of gold around other markets..