It’s outdated, not obsolete. It’s outdated because it doesn’t incorporate numerous lessons that more modern systems have (in particular, coherency in the sense that Chronos used).
It doesn’t follow. Nevertheless it is already true that the US government mandates which system(s) you must use. Depending on the application, you are obligated to use US customary units, SI, or both. You do not get to use UK imperial units, or traditional Indian measurements, or any of a zillion alternatives (at least not without also providing the legal units, with requirements about size and visibility).
So, why do you get worked up at the idea of being forced to use a certain system units when you are already being forced to use a certain system of units?