It's not just obstinance, switching everything to metric in the US would likely cost billions (if not trillions) of dollars. And other countries that have made the switch have often ended up with weird Frankensystems of measurement, like the UK where they mix metric and imperial all the time (plus the weird UK-specific measurements they have like "stone", which is based on the pound).
https://en.wikipedia.org/wiki/Metrication_in_the_United_Stat...
One does have to wonder what it is about Anglo countries specifically that makes it so difficult for them, though. Well, Canada at least has the excuse of being next door to US, with the resulting economic effects. For UK I'm pretty sure it's just about not being like "the Continent" at this point.
A huge percentage of those countries didn't have established industrial bases, infrastructure, etc. And also no educated general populace that needed reeducating. And often those countries were effectively forced into adopting metric through colonization and/or invasion.
This is not true and that's trivially verifiable.
No calculator, no references, no Google:
How many inches are in 5 and three-quarter miles?
How much does 5 & 3/4 gallons of water weigh?
Except they didn't actually, see my points about the UK (similar points apply to Canada).
People get very worked up about it too. People got very worked up about a government proposal to allow people to put imperial units on food in larger type than metric (at the moment it has to be metric larger - or at least the same size).
Everything in engineering and science has been entirely metric since the 80s.
Some of those "Metric martyr" types, the kind of people who think anything which changed after they were 35 is an abomination, but somehow anything which changed ten years before they were born has never been any other way, will vandalize legal stuff which uses (in their opinion) the wrong units. So if you put a (legal and reasonable) 1.5km distance sign on a cycle route, but some car driver who thinks sane units are fascism sees it, they might smash it to pieces which is annoying.
There has been a very gradual lean towards sanity, after all my mother was taught decimal currency because it was forthcoming when she was at school, her parents had used a non-decimal currency system. When I was a teenager I still had coins which, though they were treated as their modern decimal value, if you read their faces had a non-decimal value printed on them, because it's too expensive to replace the currency when you switch.
When I was a child I would buy a quarter pound of sweets. At the turn of the century I'd ask for, and receive, 100 grams or 200 grams as I felt, but most customers would use pounds (although legally they'd be served in grams). These days everybody else would likely also ask in grams. So it's changing, it's just very slow.
OTOH on road sings, US at least seems to be using miles alone consistently, so you end up with labels like "1 3/4 miles" every now and then, which I find to be difficult to parse quickly.
I tend to think in metres at that scale but a yard is near enough.
And sure, of course metric isn't necessary. You can also write all software in COBOL and PL/I. But over the long term, the convenience of having a self-consistent system based on a few simple principles rather than historical precedent adds up.
Anything to do with STEM is metric.
Milk is also allowed to be sold in pints, traditionally glass bottle re-usable milk bottles were one pint.
It is also usual (but not legal) to sell a pint or a half of various soft drinks, in theory you should be sold these in some other way, I always say "large" or "small" but in practice ordinary people say "pint" and after all the staff will probably more or less fill a pint glass so, whatever.
Spirits (e.g. gin) are measured in either 25ml or 35ml shots. An establishment can choose either, post which one they picked and use that consistently. Why two seemingly unrelated sizes? Well, historically there were two different non-metric sizes permitted in law, and when the government legislated to make these SI units there were lobbyists demanding they allow this to continue despite the opportunity to rationalize.
As in the US, containers you purchase in a store are labelled, but here the labels must prominently show SI volume units and EU-style value metrics are required on shelf markings, so e.g. 10p per 100ml of Coke is a good price, maybe the Pepsi is on a deal for 9.5p per 100ml, the store's terrible own brand is 5p per 100ml. This EU strategy prevents people screwing with sizes to make you think you're getting a better deal, that cheaper bottle may look like a good idea but hey, it's 18p per 100ml, ah, it's slimmer in the middle which makes it actually much smaller than it looks.
