Society is rather transient.
People get new jobs, meet new people. Pursue different things. The best friends and relations of my life, and certainly most of the good memories I have, are rooted in this place where I live presently. They are rooted to my activities and my job. But if I ever get the job I really want, it could be 500 or a thousand miles away, and I'll have to leave.
It's not because I don't like the people, but I have to pursue my dreams. I will always remember this time of my life fondly...and it's that memory that is the reward of it all.