I think there is a very good reason for Nepali kids who are born here/brought here as a kid to not speak nepali. I have a cousin who was born here.. and she is about 7 now. She speaks only english too. The reason is- when she was a kid my uncle taught her how to speak in Nepali. During her pre-school and school times, she would sometimes talk in nepali. It was very hard for the teachers to communicate. Sometimes they had to call my uncle/aunt because of the communication gap. Due to this reason my uncle/aunt had to make her speak in english all the time. (Once she wanted to go to the bathroom and kept on saying 'susu ayo' and crying and no one could get it.. was a mess!!) Another reason might be due to social group. When I was 7, I came to the USA for the first time. My parents wanted us to talk to our mom in english so that she might improve her accent, but we would completely refuse. We never spoke anything else than Nepali. I stayed in USA for 2 years and my Nepali was already poor by the end. I DID speak Nepali but the reason I could not retain it as good was bacause I had no nepali friends. I would speak english in school, with my friend, with my playmates and neighbours after school! There would hardly be time to speak the nepali language. So I was more comfortable with english BUT that changed when I went back to nepal. And for spanish kids to speak spanish... Well that language is like the second language in USA. Almost everyone speaks or atleast majority understand it. So they have it easy!!