The metric system is also arbitrary shit and they both also work. And I got news for you, the Democrats controlled the house and senate in those years. They could have easily passed a law requiring everyone to switch to the metric system. But it was decided that allowing the switch over to happen organically was the better way. Maybe they were right, maybe they were wrong.
And make no mistake, while US Customary will eventually fade away, so to will the metric system in time. Just like ALL the other measuring systems in history.