Something I never thought about is that there are differences between metric countries too in usage.
E.g. in italy you refer to a glass of 200ml, 100 grams of pasta and two hectograms of parmigiano, while in hungary they routinely use deciliters and decagrams, which I'd never seen outside of school.
And the beauty is that you are still able to easily convert it to the type you are used to. I, as a Belgian, might blink once when you use hectogram, but it is trivial to convert it to what I am more used to (say kg or g).
And as ward has pointed out, it is so easy to convert between them.
On the other hand I don't understand for examples why in the US they still use measures like "cup", "oz" "pint" in cooking. Should I buy a specifically sized "cup" to cook a us recipe? :)
By watching UK television it seems that even they are using kilograms, liters and also Celsius for oven temperature, and some weeks ago there was a UK famous baker talking with some US guest and saying almost the same thing.
This is exactly why metric is so powerful: I also have no inherent concept of a deciliter or decagram, but I can convert to my understood liter and kilogram in moments.
E.g. in italy you refer to a glass of 200ml, 100 grams of pasta and two hectograms of parmigiano, while in hungary they routinely use deciliters and decagrams, which I'd never seen outside of school.