It's probably a balance thing as the stone is the commonest resource node but I haven't noticed anything sticking out as requiring stone as a material.

Obviously concrete but how much stone makes how much concrete.?
TBH I'm not at that stage yet but it's easily overlooked.

Remember there's 4 nodes mined from rocks now and with a 50% chance of that being stone you may become over stocked with stone if each node gives 15.?

It seems to be more of an accident than intentional balancing. And since the stone has to contend with coal and copper it would be unnecessary. Becoming overstocked is a problem the player should handle as it pertains to inventory and material management. Though it probably wont change anytime soon.