If SI units were as ideal as you pretend, they wouldn't have to. Imperial measure will be all but eliminated by market forces anyway, not just because SI has been the official language for more than half a century but because it is easier for business from both a technological and marketing point of view. Grams in particular are a boon to surreptitious shrinkflation.
None of that gives an excuse for a dictator to prosecute a farmer for selling spuds at the gate by the half cwt.
You can drop a few grams from say 49g to 41g and people won't notice but if you try and go from 1/4 scruple to 62/268 of a scruple people will see right through it.
I’m going to guess the (in my mind incorrect) premise is that in the case of price changing concurrently with quantity imperial units make the value—“price per”—calculation easier. Edit: it'll only get better once we return to guineas, crowns, shillings and farthings
If SI units were as ideal as you pretend, they wouldn't have to. Imperial measure will be all but eliminated by market forces anyway, not just because SI has been the official language for more than half a century but because it is easier for business from both a technological and marketing point of view. Grams in particular are a boon to surreptitious shrinkflation.
None of that gives an excuse for a dictator to prosecute a farmer for selling spuds at the gate by the half cwt.