Life can take us on different paths so lots of old friends and family who drifted apart for no real reason than we went different ways, had different priorities, obligations, etc.
Reconnecting with someone from a different phase of your life is a bit chancy in that it may be like an intrusion, or that you both migrated enough to practically erase the connection.
I have an interesting old HS classmate (we graduated 60+ years ago) who started emailing me about 25 years ago, professing his great memories of our childhood together, wanting to make sure we didn't lose our connection. So I write him back, filling in the years since, and ... NOTHING; he doesn't respond to my response, for another 5 or 6 years when he starts the cycle over, professing his great memories of our childhood together, etc. After 4 cycles of this he died. Every 5 or so years he'd email, I responded, then 5 years later he would write again, as if the previous exchanges never existed.