No other base units have a prefix, so why does mass?
In: 188
Because for actual human measurements a kilogram is more useful. You could say the same for a Calorie with is actually a kilocalorie, but calories are so small they wouldn’t effectively convey dietary information.
Aside from the original reason, there is no real incentive to change since you wold have to either rewrite every paper or manual containing grams or check whether it was printed before or after the change which is much more laborious and costly than typing an extra k.
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