[crote]

Exactly: the entire world has a standard, and the US is doing its own weird thing.

The long-term gain is being able to sell your stuff to the rest of the world, and being able to import stuff from the rest of the world without paying a Weird Format Tax.

Would you rather manufacture stuff for 8 billion people, or for 340 million?

[SoftTalker]

You could also argue that North America should convert to 50hz 220VAC for electric services, so that one line of products could be sold to the entire world. But the switching costs would be huge and manufacturers generally have no problem making the few changes that are needed to make products for export, or when possible designing their products to accept either standard.

Cutting metric or imperial threads in a pipe fitting is a programming code change in a CNC machine, and maybe using a different cutting tool. Easily done for an order that's going to be exported.

So I don't think manufacturing is a big concern, and not the reason we've stayed with old standards in many cases.