My informant used to receive Chinese red envelopes when she was a child growing up in San Francisco in Chinese New Year. On those occasions, upon receiving them she would give some traditional Chinese greeting like 恭喜发财 (Geng hei fat choi – congratulations and be prosperous) and 新年快樂 (sun li fai long – happy new year). She says that there were lost of other greetings she said but she couldn’t remember them very well anymore. But after she reached sixteen, her parents stopped giving her envelopes, she assumes that they forgot, and she stopped asking for them because she thought that it was rude.
I think that the parents of my informant stopped giving her Chinese new year envelopes because she reached an age where she no longer needed to ask for them. Also, I believe that her family, since she and her parents had essentially grown up in San Francisco, there was less urgency to keep up a Chinese tradition which had no place in modern American society.