With so many cookbooks and recipes coming from the US, it would probably lead to quite a bit of confusion to convert cooking measures to metric. Much like with construction materials, there will probably be a lasting imperial legacy when it comes to things like how butter is sold.
My bet is that a lot of the irregular measures for various consumer products like butter is due to holdover machinery from the imperial days, or even the fact that in the USA-Canada context it's impractical to produce metric-centric machinery just for Canada. Though obviously metric-centric butter machinery exists all over the world.
I've always suspected that the 4 litres of milk in three bags (and not four, or some other more logically metric set-up) was because of this as well.
There are also the odd old road signs here and there that have "1.5 km" as the distance to an exit and that used to be "1 mile to exit signs". In this case 1.5 km is obviously an approximation. Who's counting?
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Even more annoying, is when imperial breaks down into units too small to be fractional, and they admit defeat and use 1000ths of an inch anyway (confusingly, called mils). So they know deep down that the decimal system is what makes sense, but are too stubborn to let go of the archaic system.
Yes, calling a thousand of something "mils" is really confusing. The word "mil" and "thousand" have nothing to do with each other!