Why do we say 17,000 kilometers instead of 17 megameters?
And instead of (metric) tons, I want megagrams. No kilotons; gigagrams.
I remember the first time I got those units out of gnu units on the command line scratching my head wondering why I'd never used them before and why it was using them at the same time.
atto-lightyear = 1e-18 lightyear
lightyear = 3.156e+7 lightsecond
Hence, atto-lightyear = 3.156e-11 lightsecond = 31.56 pico-lightsecond
Hecto = 100
Hectoliter = 100 litres
Hectogram = 100 grams
Kilo = 1000
Kiloliter = 1000 litres
Kilogram = 1000 grams
The only 'commonly' used unit of measure larger than a kilometer is a light year, at least that I can think of. Maybe a Astronomical Unit, but not 'common' I suppose.
But it shouldn't be common.
If the data consists of electrical potentials between 0.0000001 and 0.0002 V, it’s way easier to think about it as microvolts, especially if any other is in a complementary scale.
I've had people get angry when I tried to use Mm (mega metre) or ask why using some currencies symbols before the number when all symbols for all other units are used after.