I second the sibling comment: not emigrating is no guarantee that your language is safe. For example, there's a long history of trying to suppress the Ukrainian language [1], and until very recently, the Irish language was dominant in Ireland, but is now nearly extinct [2].
Back of the envelope maths here, but there must be hundreds of millions of people in Asia who can't speak the same language their grandparents spoke.
Public schools seem to be a big factor in languages dying off. But you also can't ignore the prestige factor - "my native language is small/backwards/insular/unsophisticated, if I want to get ahead in life I better speak the prestige one and teach it to my kids".
I am one of them. I speak a language that is not widely prevalent in my multi-lingual country. I never grew up around people who spoke it (except family members). My command over that language is poor, but my English is excellent. I speak in that language with my grandmother because I don’t feel judged for not being fluent in it, and I genuinely want to learn the language. But I don’t speak it in front of other people who know this language.
[1] https://en.wikipedia.org/wiki/Chronology_of_Ukrainian_langua...
[2] https://en.wikipedia.org/wiki/History_of_the_Irish_language