I am still in touch with two of my former colleagues, none of the others have bothered to respond to my efforts to keep in touch.
This is apparently a feature of modern life - if you move away, retire or change job those you used to know seem to assume that there will no longer be anything you can talk about.
Friends don't "stick around" any longer - they "move on with their life" and now that no longer includes keeping in touch with former colleagues, friends, your only remaining aunt etc.
It costs less, emotionally speaking, just to be thankful for the few that remain, rather than be upset about those who no longer care to know us, although, I will admit, it cost me an effort to accept this feature of modern life.