Friends or rather the lack of them

I was driving through town one evening and a group of men dressed in causal clothing were obviously heading out to a bar together.

They were all ages 60+ and looked comfortable together, as if they'd been doing this for years/decades.

I said to my wife that I can't seem to justify the effort to maintain a friendship like that. Even at school I had a very limited friendship group which pretty much vanished once life started to get in the way (work, relationships etc).

My wife said "that's just the way you are" and that pretty much ended that conversation.

I don't know if it's my definition or friendship. I obviously am aware of others in my limited circle. I work and have work colleagues that I get along with but I'd never want to socially interact outside of work.(I do get invited out but I decline) 

I have very limited interest in anyone outside my own household and that includes immediate family.

It does feel a little isolating at times I suppose. 

Anyway forgive the ramble