I dont find that to be true at all.
I grew up/ and am currently living “in town”, I am also of the last in my grade to get married and most of my High School friends moved out of New York, I rarely keep in touch w any of them.
My “new” and close friends are my co-workers/school friends (other than H.S.)/people that you meet as you are going through life. Many of my new friends arent even my age, but thats what happens when you leave school.