Ways People Can Unintentionally Leave Friends Out Of Social Events
Sometimes socially inexperienced people can interpret certain situations as mean-spirited or rejecting, when they're really just harmless misunderstandings, or benign thoughtlessness from others. One area where I think this can happen a lot is when someone is unintentionally left out of a get together. They weren't invited, or didn't hear about it in time, but there was no harm meant by not including them.
Of course when you're the one who didn't hear about a great party until Monday morning it's not hard to feel bad about yourself and wonder why you weren't invited. Especially if you're already feeling socially awkward and out of the loop, it's easy to think insecure, self-deprecating thoughts. More socially at ease people usually shrug these things off and understand they happen from time to time. It's tricky to give the exact reason a person gets overlooked in any one specific situation, but in general here are some ways people can be unintentionally left out of a group activity:
The person was invited, but assumed they weren't
There are true cliques that are closed off and exclusive. There are also groups of people who like each other's company and spend a lot of time together, and who are falsely assumed to be cliquey. They're just close friends though, and aren't looking to exclude anybody. They'll happily accept new members into the group, but some people don't try because they think they'll be turned away. Maybe the group is a bit intimidating in the sense that they all seem so comfortable with each other and have a lot of in-jokes.
This leads to these crossed wire scenarios where each side makes faulty assumptions about what the other is thinking, and the end result is the opposite of what everyone actually wants. For example, everyone in a "clique", maybe at an office job, is having lunch and saying, "Why doesn't Nicole ever come join us? She'd be fun to have around. She has to know she's welcome any time." Meanwhile Nicole is eating elsewhere with one other person, stewing about how snobby the clique is and how they never invite her over.
When it comes to social events you get similar misunderstandings. Everyone will be hanging around someone's apartment saying, "Why didn't Eric come out tonight? He knows he's invited, right? I'm sure he was around when we were all talking about it." And in Eric's mind he sees himself as the odd man out.
The plan was spontaneous and the people making it didn't think to invite anyone else
Sometimes a plan is hatched on the spot. Three friends could be out at a restaurant and suddenly decide to go clubbing later that night. Just the three of them go out and don't contact anyone else to bring them on board. When the photos of their Saturday night appear on Facebook though it's easy to think, "Well why wasn't I invited to that? What's wrong with me?"
The plan had an unspoken open invitation
When a group of friends do things like grab drinks after work or class, or meet to play a pickup game of basketball, the event often has this unspoken offer that anyone who feels like showing up is free to do so. If a person isn't aware of the open invitation they may feel excluded and wonder why no one ever invites them out to those pub nights everyone always seems to have such a good time at.
The people only made the plan with the friends they ran into in person
Within a larger group of friends certain subgroups of people are more likely to spend time together day to day. Maybe they all work at the same job, or have a bunch of classes together. When they came up with a social event they may have talked about it when they were all in person, and fleshed out the details then. Then, with the plan set for everyone who was there at the time, they didn't really tell anyone else. It wasn't that they had anything against their other friends, they just didn't let them know for whatever reason.
A plan was made among a few friends, who were then lazy or forgetful about getting other people into the loop
It's the 'benign thoughtlessness instead of malevolence' idea again. Sometimes a bunch of people will make a plan, say, "Let's all meet in the park on Saturday afternoon", and then just not get around to letting everyone else know. They already know they're coming, and that at least some of their friends will be there, and that things will be fun even with just that group, so they're not super motivated to get the word out to every last person in their social circle. This is particularly true if someone's group of friends is pretty big. They can't realistically tell a ton of people about everything they do.
It just felt like too much work to let everyone know about the plan
Similar to the point above, sometimes some friends will make a plan, and realize it would be good to invite more people, but after a point the idea starts to feel like too much work. If there are ten other people you could potentially invite, the idea of texting all of them, and then texting back and forth about a ton of little details (time, place, directions, "Umm... yeah, maybe we could make it a potluck, let me check with everyone else") can seem unappealing. They think maybe it's easier to just leave things the way they are, or maybe hope someone else spreads the word to everyone else.
People meant to invite them, but there was a mix up
Sometimes in the hecticness of planning an event, especially one with a fair number of guests, people can fall by the wayside. Maybe the person's name accidentally got left out of a mass text/email/Facebook invite. It's also possible that several friends each thought someone else was going to tell that person, and as a result no one ended up doing it.
The people making the plan didn't want a bigger outing, so they stopped inviting people once the main group was settled on
Larger social events have a different flavor and dynamic to them. Sometimes they're fun, but at other times when people are planning a get together they have something smaller and more low key in mind. That, or it's the type of event where having more than a certain number of people makes things unwieldy. However it is the few attendees are decided on - maybe they were just around to get invited at the right time, or were the ones who made the plan in the first place - no one else is invited after that. Again, nothing personal against them, the planners just had a certain type of event in mind.
Once people had their invitations they didn't go around alerting everyone else
Someone may have not planned a social gathering, but once they know about it they don't really see it as their responsibility to make sure everyone is in the loop about it. Although it's probably not even conscious, their thought process is: "I found out about it, I know I'm coming, and it's everyone else's own responsibility to stay in the loop if they'd be interested in something like this as well."
People don't feel like mixing their groups of friends
The idea of mixing different groups of friends is a whole other topic in itself, but for now, sometimes when people make a plan it's among one group only. Of course they still like their friends from other circles, but see it as too much hassle to try to combine them all for this particular outing. The idea of mixing groups could also extend to something as simple as some friends wanting a girl's or guy's night out. Here it's easy to see that it's nothing against you if you're not invited because you're the opposite gender.