Over years I've given up on trying to be a social person and I just need to be honest about it: I hate socialising and will only do it when there's a clear and direct reason for doing so. The biggest reason is sex. Once that's not needed the reasons for doing so are very few and far between.
It makes sense in a way and you are the way you are .. but I think you might benefit from trying to open yourself to new experiences, unless you want to repeat the cycle again and again. (Oh and I don't mean casual sex. Rather something like interacting with people in a way you have not before, which is easiest by going somewhere you have not been before.)
People tend to make friends naturally this way over time, but even if you don’t, at least you are doing something fun and developing a life independent of your partner.
Instead of friends I rely on my mental health, my skills and the financial system for insurance. It would be a big mistake for me to let my health deteriorate, get married or quit my job, for example.
Well my point is to find something you enjoy doing and not worry about liking or socializing with the other people there. You can find the others annoying and they can find you quiet and unfriendly at first, but if you keep going regularly there’s a decent chance you’ll click with some people eventually, even if it takes a year or more.
I get the motivation and timing issues though. There is definitely a hump to get over in establishing a new habit.
From my point of view everyone does the same, but can't deal with the isolating nature of it all and need to decorate it with friendships and similar unwritten rules and then act surprised when they don't work
Friendship is when everyone comes with a random set of expectations, all of them differing from person to person, and get disappointed when it doesn't translates to reality.
That's the key here. Most people want money because, contrary to the old adage, money buys happiness. People want friends for the same reason: friends are the people who you are happy to spend time with. Pretty much any activity can be made more enjoyable when done with people you enjoy spending time with.