My family has been speaking English for over 100 years (My family predates WW I in the US) . They have eaten and breathed English since around the year 1900.
Frankly the fact of the matter is the world is getting smaller , people need to comunicate with each other especially from other countries. Languages are disappearing as people need more world languages.
Very few peope speak Yiddish anymore, its a hinderance instead of a help. And if you want to tell me its the Jewish Langua Franca, Actually its Hebrew not Yiddish today. I speak Hebrew and have used it to speak to jews from other countries many of whom werent even Ashkenazic