Mining "perfectly" only matters against top-level competition. Otherwise, just pointing a decent number of harvesters toward the resources (SC) or setting work

Mining "perfectly" only matters against top-level competition. Otherwise, just pointing a decent number of harvesters toward the resources (SC) or setting workers on auto (Civ) is good enough. So you have it exactly backwards; mining efficiency doesn't matter much to newbies. As for why resource mining / management even exists: from a warfare perspective, because you can only fight as long as you have the tools to fight with. From a gameplay perspective, because acquiring resources provides a major motivation for leaving your secure base, and the cost and risk associated with setting up a secondary base (versus using the same resources for some other objective like attacking an enemy position) provides a major decision point. Learning the tools -- how to harvest, how to build units, how much your units cost, etc. -- is newbie stuff. The real game is in setting yourself up to win the war through the engagements you choose. The real game is in deciding which resources and technologies to pursue, when and where to engage your enemy with which forces, what risks to take at what time, how to respond to failures, what sacrifices to make for the sake of an objective (intelligence, delaying an enemy, destroying or acquiring something, etc.), recognizing the right time to press an advantage, and so on. It is the stuff of warfare, and the stuff of life. Far from an Excel optimization exercise, it's a rich multi-dimensional decision space with several paths to victory based on numerous factors that can vary from game to game. That's why my wife and I still play Starcraft after twelve years.