I can’t speak for other cultures but fear plays a part here (San Diego.) I grew up here and only moved away for two years in college. All of my college friends, except one, have moved away. Some wanted to experience life elsewhere. Most were forced out by the rising cost of living.
I was at dinner on July 3rd in Longmont Co, with one of my oldest friends and my girlfriend. I lamented to both that I really felt deeply disappointed by my friends leaving and my inability to find new ones to replace them. My fear is not being able to find those relationships. What my friend and girlfriend pointed out to me though was that I had high expectations. Lots of people aren’t willing or able to meet those and so in a way I was sort of doomed. I thought to myself, “high expectations?” I think what they meant is that most people have a latent fear of opening themselves up to others. As we get older it becomes progressively more difficult. It becomes harder to bridge the gaps between ourself and other people. Our moats get bigger, our bridges get shorter.
I have always thought that deep meaningful close relationships with others was the most important characteristic of a successfull life. That and health. On the plus side, if you are looking for a good friend, I have spots available!