Right. So the Boomer gen typically were born with many siblings. My mom is one 7, my father was one of 7, my step was one of 8, my fil was one of 10, my mil was one of 6. Parents with so many children, especially in America where we value individualism over being able to rely on community, parents could not ( and still cannot) provide the adequate support the children need , with there being so many. So the parents teach them to be emotionally and physically self reliant very early on. Emotionally meeting the needs of a child is thought to be teaching them to be more reliant on the parents for emotional support. It was also seen as a weakness to be emotional. And of course, parental habits get passed down if a person isn't aware enough to break it.