>>11308912its the same reason why engineers don't need to know the most advanced physics and for the most part work with the stuff that was discovered 100~200 years ago. For the vast majority of cases we don't work with the infinitely small or large cases. If you wanted to design a beam when accounting for each and every particle and their interactions you would be stuck forever trying to solve a problem another engineer could solve with a simplified model and you would both end up with around the same result.
