Yiddish speakers today are mostly ultra-orthodox Jews. The language binds them together across country boundaries, and cuts them off from the surrounding society. Even in Israel, which runs on Hebrew.
This is recently relevant as the Israeli Supreme Court recently ruled that the draft exemption for the ultra-orthodox must end.[2] Many will speak only Yiddish. The IDF has a crash one month course in Hebrew for foreign Jews who want to join and some other ethnic groups, so they will cope. Israel nominally has compulsory military service, but the ultra-orthodox have been exempted so they can supposedly study Torah. When that started in the 1940s, only 4,000 were in that status. Now it's 1.4 million. There's currently political unrest in Israel over this.
[1] https://www.jpost.com/Features/In-Thespotlight/A-bisl-Yiddis...
[2] https://www.msn.com/en-us/news/world/after-court-ruling-ag-t...