Just to add another comment echoing the many that have already been made.
I don't think I've ever been involved with a group like that. The nearest I have to that is a group of friends that I have made from a hobby that I participate in. It is very social and when we are involved with the hobby we are very often there as a group.
However, outside of the hobby, I never see them. And that's absolutely fine. (Just like when my DH plays rugby - for the (very) seniors team - they have a great time when they're together but rarely see each other outside of that)
When I was at school I had a best friend right from the first year (year 7) through to the sixth form. I obviously had other friends, but I do remember, even to this day, my parents telling me that at an annual parents evening, a teacher admitted that he wasn't too sure which one I was as the two of us were always together.
At university, I studied a very STEM subject and lived in an intercollegiate hall of residence.
So my friendship groups were a mix of people from my course (mostly male) and also from the hall. I did have a couple of close female friends where I was staying in the first year that I later kept in touch with but we weren't really "the girls". The same in the third year.
What also affected the balance of things was that one of my friends on the course started going out with a guy in the physics & astronomy department, So quite a few of us started hanging out with the physics & astronomy guys (not least because their common room was directly below the Student Union bar).
So, certainly at school and university, I have never had "the girls" and have usually had groups of friends that were often more men than women.
When I started work it was in a very technical role and most of the people I worked with were men. So it was more a case of "the lads" rather than "the girls".
But, to be totally frank, I do really enjoy having an entirely female group of friends in this hobby (even though there are many men also involved in this hobby).
But that is just one part of my life; the rest of my life involves many different people of both sexes and I'm quite glad that it's not confined to just one small group of people.