All of those have historical roots. Screws use the ought gauge because they were made from wire which came in those sizes. Not because it is arbitrary, because there was no metric standard, and your wires and bits had sizes based on wire sizes. All these measures are slowly being forced out or realigned with metric. We no longer get a pint of soda, we get some number of millimeters and a strange fraction of ozs. Definitely one of those odd useless hills to die on.