[RugnirViking]

I think the important distinction here is that the UK is definately on the path to transitioning away sensibly in that imperial units haven't been taught at any school at any level for many years. All product units (litres, kgs etc) in shops are given in both metric and imperial, with the metric part required by law and the imperial part there for old people's convenience.

[kd5bjo]

In an odd way, the US is fully metricized: they’re one of the original signatories of the Treaty of the Metre, and redefined all of their legacy units in terms of SI ones [1]. SI units are used directly in the sciences and most products have the SI equivalent listed alongside the traditional measure. I understand that industries with international supply chains, like the auto industry, are also mostly metric these days.

There just hasn’t been much of a reason for the purely-domestic parts of the market to switch: house builders are looking for 2x4 lumber, and won’t buy from a lumberyard that calls it 50x100mm. Knowing that, the sawmills continue producing the 1.5x3.5 inch profile that’s called “2x4” and anything else is a specialty item. Who has an incentive to push through the change?

[1] https://en.m.wikipedia.org/wiki/Mendenhall_Order

[beojan]

> and the imperial part there for old people's convenience.

And also because that's what was used to actually design the container. Milk bottles in 1 / 2 / 4 / 6 pints (imperial pints, not US pints), 454 g jam jars.