Most of our non-Caucasian parents in the community come from "back home" and we, their offspring, are the first generation of American born/raised/both in this country. So we happen to be well acquainted with how things work back home because our parents express it in the community. For the most part.
Anyways, I never did this because I HAD to. I just think it's polite to do so and rude to ignore my mom's friends. Plus, I think in Islam you should greet everyone. Like when a person walks into a room he should greet everyone. I think you can give a big hello to everyone but our culture likes to take it a step further a greet every single person...?? And the young should greet the old first, the smaller group should greet the larger group. Stuff like that. So I always do..if I can recognize them.