Groups. Why?

Been bugging me since last year, the thing with groups and people being left out. Was out having dinner with "The Kid" today, at Chom Chom as usual. Were talking bout' the usual stuff, cars(well only i was going on and on about that), games, murdering people, random wanton acts of violence, military stuff and the glorious past. So we were just talking about such random stuff when we drifted back to talking about the old times, and i forget what we were talking about but suddenly he said something like "Oh forgot I'm not part of your group". Now hearing that being said aloud for the first time really struck a chord with me, as we all know i feel that if there's some occasion to be celebrated or a gathering to be had for whatever reason the more the merrier. Unfortunately the people who think this way are a pathetically few minority, and now i ask this question, why is this the case? Sure i know that people and their groups usually try to limit the amount of friends so that there will be a balance of sorts and that those with a ridiculously low self-esteem of themselves will feel that as the group gets larger the less time there will be for his friends to pay attention to him. Now i will proudly state that i was never tight with any group, me being a wanderer as such, i only joined if asked to and am not thick skinned enough to impose myself on others, so of course there were often a many times where i was left out. It's like "Oops sorry we forgot about you", but of course i take such petty things in my stride. If my presence is not wanted than it will not be there. Besides if i really wanted to be arrogant I'll say things like "You should be thankful that I'm lowering myself to your status to interact with you". Friends. This is what they call themselves, but they will not call you out if they feel that your presence will be inconvenient for them in any way. Friends. This is what they call themselves but they will not offer you assistance if they feel threatened by what you may accomplish. I've had kinder enemies than these kinds of useless friends. In fact I'm ashamed that i even thought of such distasteful people as friends, like how the hell did they get pass my screening? If anyone should be accused of being arrogant it should be these kind of screwed up people who will only talk to you whenever they feel like it. Jumped-up shits. Then of course there are those who feel that as they are older they have the right to talk shit to you. OK, you little prick you might be a bit older but i can bet my arse your sad life has been a right bed of roses, gone through what i have before you accuse me of being anything little shit. So to groups i say a right FUCKING NO! The thought of leaving some of my friends out sickens me and tarnishes my honour. To the kids i don't belong to any group, and if any a group i wanted to be a part of it would be yours, the kind where age doesn't matter, the kind where more is always merrier.
"Keep a closer eye on your friends rather than your enemies, because only they can stab you in the back, and it would most certainly hurt more"