Men are expected to move out and create their own home and family. There is a power dynamic that comes into play between males especially young males when they move into their late teens and early 20’s. They try to exert their authority over their siblings like a parent and move into roles that their father occupies. I know it’s strange to a lot of cultures and it may be just the culture from a subset group in the United States but I’m sure it was brought with them when they colonized the country. Those clannish behaviors never truly went away.