[tokinonagare]

> Even Japanese, a language used by 125 million, has similar issues, my Japanese coworkers frequently switch to English during technical discussions.

Are you Japanese yourself? If not I don't think it's strange that they would adapt their way of speaking with a foreigner, especially since most technical words in IT are coming from English anyway. For other fields, health for instance, it's totally possible to never heard English in months/years. Japanese is well alive, and English is more a social marker than anything else. Most Japanese have very bad command of English if at all and can live their whole life never using it.