Part of it could be getting older. I’ve found that people drop off gradually after school/uni, following different paths, moving away, having kids etc. Then making friends is much harder as we get older. Everyone is busy and often have no time or want for new friends. It takes repeated meeting and socialising with same people to make new friends. Outside of sports groups, religious institutions, or parents groups there’s not much opportunity. The older I get the lonelier I get. It’s hard.