You can see the effect all the down to something as small as 4 friends who have met once a month for 10 years eventually having to break up due to life getting in the way, and the feeling that not only is it going to be sad to not have these meetings any more but the feeling that there is some sort of almost-concrete entity that is somehow being hurt and needs to be defended, as if there is some obligation that has been created independent of the four participants that is being violated beyond the mere summation of four people's personal feelings. Humans build these structures readily and often defend them beyond what rationality may suggest.
What you're describing is a durable social system. Social systems are what humans evolved to survive. We're squishy, relatively weak, hairless apes that walk around on the ground. Alone, we're easy prey. Together, you get... well... gestures widely.
If you invest the time and energy into creating a social system, it's perfectly rational to keep it going as long as possible. Otherwise you expose yourself to more and more risk as you go through the world, and must expend more time and energy finding another one, if that's even possible. Before humans built larger societies, that could mean death.
But yes, if a system fails to prioritize its continued existence, it doesn't matter what else it accomplishes, it will cease to exist as that system.
By what measures would other systems of social organization measure their success and why aren't we choosing them?
1. https://knowyourmeme.com/memes/we-investigated-ourselves-and...