It is mostly just habit and wouldn’t take that long to change. In the 1970’s the US started the process and if Reagan hadn’t been elected President, the change would be “history”. The metric changeover was supported by Carter, so of course the Republicans had to say it was a bad idea. The solar collectors on the White House had to go… I’m surprised they didn’t outlaw sweaters..But for everyday use, there are two small advantages to the current system in the US. With volume, it’s all multiples of two, and that can be handy. And a foot is divisible by two, three, four or six. That doesn’t seem like much but does come in handy sometimes. Still it’s not enough to make up for the dis-advantages. Anyone know (Without Google or Wiki) how many feet (or yards) in a mile? And how much does a gallon of water weigh?