I think that the issue is less to do with the family and more to do with the fact that as an adult most of your adult interaction comes from your profession. Your friends as a child and young adult come from school, as an adult they only come from social groups that form around things such as sports, hobbies, and social groups such as a church.

With a move to first world status there is usually an associated decrease in religious adherence. People then naturally define themselves as what they do first. Getting friends as an adult is very hard as competing schedules and interests can conspire to push people apart, so the default is to make friends with those with whom your work. As a stay at home parent that requires actually seeking out the parental groups.

tl;dr making friends as an adult is difficult and can lead to loneliness.