Mother kept it to herself, mostly, so she could converse with her sister without anyone else knowing what they were saying!...on the phone or in person!

My parents did the same with Polish, WO'N. They wanted to be able to talk privately in front of the kids! There seems to be a different mentality today, with more people recognizing the value of multilingualism (except of course for my own kids, who were exposed to weekly Spanish lessons at school starting in kindergarten, continued the language through high school and were supremely relieved to test out of the language requirement in college!).