Fun probably-already-known fact: NASA accidentally destroyed a $200 million Mars orbiter from of a missed imperial->metric conversion, because NASA does generally work in metric, and some Lockheed-Martin software provided numbers in imperial (while claiming to be metric)
Didn't you see the meme: "There are 2 types of countries, those that ise the metric system and those that landed on the moon."?
It's also usually shared by the same idiots that don't realise that barley corn is an actual measurement in their beloved imperial system.
Ask any of these smart arses how barley corns are in a foot or how many feet are in a mile and suddenly you hear excuses.
Not to forget that the inch defined by the meter.
I'm not sure what your point is? Some people not knowing a certain obscure unit of measurement doesn't discount an entire system of measurements. Also your mile example doesn't make sense because most people do know how many feet are in a mile.
You're proving my point exactly. The imperial system is so convoluted that even people that INSIST that EVERYONE should use it, don't understand its units.
Just because most people don't have to deal with a certain conversion, doesn't mean that none do. There are enough engineers that design stuff which is related to problems on these variations in scale. They waste hours in productivity in needlessly complicated conversions (because fractions). Not to mention the mistakes that get introduced like the famous Mars lander that crashed because of imperial unit conversions.
Not only are the units incredibly inconsistent, you also have the issue that Brits and boat people use variation of some of the same units. US Gallons vs British Gallons, mile vs nautical mile. MPH, vs knots. That barley corn that Holzkohlen mentioned defines shoe sizes, unless of course, you don't wear shoes.