I'm 68 and I use metric (although I can use both) for everything. We do everything in metric in Britain today. I started teaching metric in primary school in Britain 1972!! So the Imperial system went out with the British Empire.
When will Duo get up to date? It's very frustrating.
It varies a lot. I went to school in the 80s and we were taught both. Our maths textbooks were ancient and in imperial and our headmaster was a mathematician who considered an over-reliance on base 10 was not a good mathematical grounding and demonstrated that the two systems work better in different situations. So I use both, I cook in imperial but am a scientist and only use SI at work.
I agree USA still uses Imperial measures. I had to use them when living with Americans in W Africa. But I'm learning Welsh to speak Welsh here in Wales - for everyday use.
Surely when learning a language of another country you want to imbibe the culture and understand the words you would use there. Here, in Wales, in school in everywhere, we use metric measures. Only some of us oldies remember Imperial.
When I learned French, many, many years ago, even although we used Imperial measures in Britain (that's how ancient I am!) we had to learn Metric because that was what was used in France.
I suppose some folks may want to use the old system but it seems nuts that when children learn Metic and have been since 1970s here in Wales, that Duo is using Imperial.
Ah well if we have elephants and lions and everyone eats nothing but parsnips in Wales according to Duo ...................
It'll keep us amused during Covid 19.