@Vinit - You've made some very excelent points. I agree 100% that it is typically a household to household, individual decision.
Call me old fashioned, unsensible, or whatever else you might like to. The fact is, as a child when we moved to the US, I never chose to leave behind my culture. For me, that culture, that language, and the traditions are all part of my identity. I also believe it will be the identity of my children (distant future😆). And so I fully intend to pass on the values, traditions and culture I was brought up in. This includes speaking in Hindi.
My mother tongue (and why do we call it "mother tongue" when our families are traditionally patriarchal!?) is Bhojpuri. Yet circumstances (army family) led to me learning Hindi and English simultaneously and picking up Punjabi as a 3rd language for the most part (good old Patiala).
My Bhojpuri is pathetically weak. And not having had the presence of dada-dadi in our lives, we never did pick it up.
So I suppose, by default, Hindi has become my "mother tongue."