Perhaps if you were just looking at the real world logic of it and ignored the gameplay loop.

Changing that would basically effect game balance and other things would need to change also.

First is skill development. You only get pickax skill when using the pickax on rock or ore or tree stumps or something... you don't get it for digging in dirt. Basically they would need to adjust the skill level development to offset the changes to needing to mine less ore.

Second is usage. If they basically doubled the output then they would likely double the cost of building in bronze. You wouldn't magically get double the output and make the game super easy they would have to adjust something.

Third is time. Once you hit black forest level you get a lot more tasks to do. Farming and taming become a thing... taking time to develop those things while you mine etc makes sense also in terms of progression.

Don't get me wrong, it is kind of time consuming and feels a bit slower paced .. but having that time to develop your skills before entering the swamp is also good. Many people post about the swamp being a big increase in difficulty already.

I wouldn't mind it being easier myself mining for bronze, but if I ask myself if that would be good for the gameplay in general I would have to say no.