Bruno, I know what you're talking about. In her late 80's, early 90's my great-grandmother wouldn't spare enough flour from her war-prep cache to make a few crepes.
I also agree with the "should" but not "shall." Other than having to deal with the elderly and people with learning disabilities, I just don't see how just making someone learn the language will help them integrate into the society. I know several people who understand and speak English when necessary, but avoid it whenever they can. They'll end up working dead-end jobs, having no prospects and b****ing about how the old country was way better. On the other hand, my grandma, whenever she visited us, she took English classes to improve her language skills even though she never intended to move to Canada. Ofcourse, she had a law degree (because tuberculosis prevented her from getting an engineering degree), already spoke Serbian, Macedonian and French, had worked for private practices and public service and held our family together. The cream will rise to the top.