Maybe they're just well-educated people with a good understanding of the vocabulary of their language - and they're not like some teenagers who think that you're only allowed to use words or phrases that were first said in the past five years, or that they use on Love Island?
It's ironic how many people rightly embrace the rich legacy that Shakespeare left us, with the many new words and phrases that he introduced or brought to wider usage; but then they scoff at other standard words that he also used - ones that have never stopped being in continual use by English speakers everywhere - and denounce them as 'obsolete' or American, just because they don't regularly use them, or because they first heard them on a US TV series on Netflix.
You might as well insist that we shouldn't use the words 'to', 'be', 'or' and 'not' - because Shakeapeare used them (so they must be archaic) and Americans use them (so they must not also be British English).
Some people just don't seem to understand that, whilst there are indeed a lot of words and phrases that are used in (English-speaking) North America but not in the UK and Ireland, and vice versa, the vast majority of our language is the same.