Obviously you have not spent any time in cities like Boston, NYC, Seattle, or any place with large populations who came to the US after WWII.  Most of those elders did not learn English because as an elder they had status in their communities for having survived the war.  Staying alive, and feeding their over were priorities over learning English.  The refuges from Vietnamese to the Hmongs  are following a similar fate: family survival first.
I'm sure your ancestors had the same priorities when the came to America.