After all, speaking one language at home and another at work is a bit of a barrier to full assimilation on the part of immigrants.
There's a friend of mine whose family is from India. They are all fluent English speakers. His parents are evangelical Christians; they went to the closest thing my town has to a megachurch. They like NASCAR and 1960s American rock music. My friend barely knows any Hindi. And yet, when I visit their house, about 1/2 of all the conversations that take place are in Hindi--and probably most of that was speaking in English for my benefit.
