It seems like we are the same age! So I also learned this a long time ago. I think it is more cultural. But since we are greatly influenced by American culture, these days in Canada, we could be following you, now, for all I know.
But, we still have not crossed the line into "you'all" or worse "youse!" Yikes, that hurts just to write it.
PS. I am not saying that having separate words for pronouns in the second person singular and plural is wrong. I just kind of thought we had more or less dumped it in English. I have heard that the young people in France do not tutoyer people anymore. Their elders are shocked! (You have to ask the person if you can use the casual "tu" or second person singular)