Sure, and that's true of feet and others too (all sorts of different regional feet) - but we standardised and that changed long ago, and nobody uses them like that any more (you'll get some non-cup measurement alongside them that breaks the ratio usage).
Cups persist, but without much standardisation - you generally have to measure if you care to know which 'cup' size you bought. It won't often matter that much, but as I said it's intellectually annoying isn't it?
Being British I don't encounter them much, just American recipes, but I generally just mentally convert as ¼l (i.e. as though a metric cup, if anyone used that) if I'm following one.
This is not true. There is the US cup, which is 1/16th of a gallon, and then there's the general notion of a "cup" which is the crap that comes with a rice cooker or whatever.
You are dead wrong. The problem most definitely isn't solved.
We live in the age of the World Wide Web and information in ambiguous units is shared everywhere simultaneously all the time.
For example gallon are still used informally in other countries than the US.
People, particularly older people, still talk about "miles per gallon" in the UK. That's Imperial gallons not US gallons. They base their feel for that volume on that.
Same with US vs Imperial pints.
Now product information on UK Amazon isn't always rewritten specifically for the UK. Often they just reuse the blurb from US Amazon without correcting the spelling or grammar to save money.
I own an old Jetboil stove I bought well before Brexit. The inside is marked in "cups".
Any guesses if those are Imperial cups, US cups or Metric cups. I mean I bought it in the UK so they should be Metric cups but Jetboil is a US company so...who knows.
This might not be a problem for you personally but it's definitely still a problem.
Read it as 'too much standardisation' of you prefer - see the rest of the sentence after you quoted. Which US cup is 1/16 (a presumably US) gallon anyway, 'customary' or 'legal'?
Cups persist, but without much standardisation - you generally have to measure if you care to know which 'cup' size you bought. It won't often matter that much, but as I said it's intellectually annoying isn't it?
Being British I don't encounter them much, just American recipes, but I generally just mentally convert as ¼l (i.e. as though a metric cup, if anyone used that) if I'm following one.