Its mathematically neat that mm add up neatly to km but for most purposed mm don’t matter in describing journeys and we don’t need to think about suspension travel in terms of fractions of km
Ah but you don’t, because metric is neater than that.
Lengths are magnitudes of metres and weights magnitudes of grams – the prefix tells you what magnitude to use.
You never have to remember how many units make up a larger unit (12, 14, 1760) because (as long as you know your milli from your kilo) it’s obvious.
Hence if I see a sign that says “Visitor Centre 500yards” then I don’t really know what that is in miles off the top of my head, but a sign saying “Visitor Centre 500metres” is easy.
a mile is a roman measurement definded a is a thousand paces
Early metric?
But why is water important? What size metric container will I need for a decagram of custard?
Is it any easier to work that out in fluid ounces?
Anyway day to day I tend to use more water than custard 😀