A lot of those are just really old-fashioned standards, and a product of their times.
We had suppers with the family as often as we could, and when we kids started having different schedules, we had supper together every Sunday. We were expected to excuse ourselves before leaving the table, which was considered good manners; our parents did it as well.
Other rules were practical, like bedtimes on school nights so it was easier to get kids up for school in the mornings. With us that only lasted until high school, then we were seen as being responsible enough to get up and get ready for school on our own.
And three of us attended parochial schools, so we wore uniforms, which didn’t include trousers for girls. I was eldest, so by the time my youngest sister was in high school, she was in public school and girls could wear jeans.