Another reason that English speakers talk about common usage is the ridiculous number of words in the language:

The RAE contains something like 93k words, including all the americanismos.

The Oxford English Dictionary contains roughly 470k words, and estimates that only 170k of those are in common current usage. So there are VASTLY more words in the English dictionary than most English speakers have ever even heard, much less could use properly. I didn’t know that the word touristic existed in English until ai moved to Spain, for instance.

So for English speakers, getting down to the 100k or so most used words means ignoring 80% of our dictionary. So when we say something isn’t common usage we really mean something between “no one has used that word in 60 years” and “I had to go look up if that even WAS an English word”.