This. It's absolutely about overfitting/underfitting. Just as our eyes see a lot more but can only focus on one thing, abstractions are just that. They focus on

This. It's absolutely about overfitting/underfitting. Just as our eyes see a lot more but can only focus on one thing, abstractions are just that. They focus on specific things. But the problem with the physical reality is that it does not end, and everything is connected. Every time we make an abstraction we are severing the subject from it's surroundings which physically are inseparable. They are only theoretically separable. Hence scientific research begins with closing an otherwise open system. Even when we weigh an apple, it's weight is influenced by the gravitational pull of the sun and everything else. Hence what matters depends on application. If you're buying apples by weight, we can safely exclude these influences as inconsequential to the price of your apples. Good enough is what is fitting, and they make good abstractions and good science. It's easy to lose track of utility in social sciences, because history only happens once, and theories often appear to have no predicting power or future use. But if anything, social sciences provide us with introspection. It tells us who we are and how we've been. If you already practice this on a personal level, then you already know how valuable this is at any scale. If not, you should begin to practice it on yourself first, because the value of things is most easily admired through experience.