No doubt inertia is the biggest thing that keeps most people in place at home.
In 1978 I moved to Oklahoma City. I did not know one single person except my grandparents. The one reason I came to OKC to look for a job was I figured I could hang out at the grandparents house on Sunday afternoon and odds were high grandma would invite me to eat with them. Lots better than my cooking. I loved all my grandparents, but they were not a lot of fun to just hang out with. Lawrence Welk was just not my type of music or entertainment.
I had to learn to navigate the city, and start to find friends and get involved with the city activities. Just like I did all my life with all the moves I made as an Air Force brat growing up. I can't image how hard that is for someone that grew up in one house, moved out from mom and dad, and lived in the same city all their life. To leave all your friends and start from scratch is not something many want to try.
I know many people that have life long friends. I live 900 miles away from the high school from which I graduated. And I only knew my high school friends for two years so non are friends I have ever tried to connect with.