> Find out how many fl oz of milk are in a measuring cup graduated in units of cups? Ask mrb.

8. Volume is base 2. Two tablespoons in an ounce, 8 ounces in a cup, (there used to be other units in between, but nobody used them, like deci in si) two cups in a pint, two pints in a quart, four quarts in a gallon.

If you were going to sell me on switching units, it would be based on hexadecimal instead of base 10.

> Convert my daughter's height from feet/inches to inches? Ask mrb.

5' is 60". Add and subtract from that. 5'6” is 60"+6" = 66" inches, 4'4" is 60"-8"=52", etc. "Normal" humans cluster around 5' so this takes you pretty far.

> Convert a package's weight from oz to lb/oz? Ask mrb.

Again, base 2. As a programmer this is easy because it leverages all the same neural pathways that I use for converting between base 10 and base 2/16. Hell, maybe learning to cook in base 2 has made me a better programmer.

> Need to know how cold it needs to be outside in farenheit for water to freeze? Ask mrb.

This is definitely the worst example. 0°F is really cold. 100°F is really hot. Fahrenheit is objectively better than Celsius as a common parlance unit.

> I lost count of the number of times they accidentally mix up for example 1.3 feet with 1 ft 3 in.

I've never seen anyone do this ever. I've seen dumb computer systems do shoddy conversions on inputting numbers into a program, but that's why you normalize your inputs and show it back to the user. I've never seen or heard of a living breathing human make this mistake.

> "six pound five"

That's like saying "100 centi 57 meters". Those words have meanings on their own, but they don't have a meaning in that order. The only meaningful response to that is to be confused, and then realize they're confused.

How long did they live in the US and how long have they lived where they are now? This sounds like someone who lived in the US until they were ten and moved somewhere where they not only didn't use customary units but didn't speak English. Then spent the next few years scrambling to master the language and hit adulthood understanding neither US customary units nor metric units.

Honestly, culture, customs, and normality run deep. Those handful of nations that use , as the decimal separator and . as the thousands (or otherwise) separator would have a much easier time and much more benefit swapping their separators than the average American would switching from customary units to SI. Nearly everybody uses a 24 hour day, 60 minute hour, 60 second minute. 3600 second hour, 86400 second day, etc.

Oh did I say 24 hour day? Well I lied but it's close enough.

Astronomers happily use astronomical unit, light-year, parsec, and z= redshift to measure distance all in the same context. For me, having "dumb, arbitrary" units is way less important than having familiar units. Despite the fact that humans are dumb and arbitrary, we're still pretty clever.

Most of the people who complain strongly about customary units, which are dumb and arbitrary, speak languages where inanimate objects have gender. (for the record, I also think grammatical gender is dumb and arbitrary in English) "Auto" (meaning car) is neuter and "Wagen" (meaning car) is masculine. If one considers a scale where 100°F is really hot and 0°F is really cold a dumb, arbitrary system, you should stop to consider whether to_lower(str) and to_lower(to_upper(str)) yield the same results.

Humans are dumb, arbitrary creatures. The fact that US customary units are tend towards base 2 units instead of base 10 is way less arbitrary than daylight savings time, or the fact that France is in the wrong time zone, or the fact that Denmark has enshrined in law its own national time basis and then completely ignores it and then refuses to change the law which is ignored by literally every single person in Denmark.