Not really. It hurts people's feelings to find out they weren't invited to something they thought they should have been. Protecting feelings and smoothing out awkward social dynamics are the the category of "very adult."
As a more general example, you wouldn't talk about a happy hour you were going to after work with people who weren't invited/aren't invited/you wouldn't invite. I believe every sitcom on the planet has at least one episode with this lesson in it.
It's both things. Being an adult means not being overly bothered if you weren't invited, and it's also very adult to prevent the situation where the uninvited friend doesn't find out, out of concern for their feelings. Both are simply approaching it from different ends.
I'm in my thirties now, and I have been on my own since I was homeless at sixteen. One thing I have learned about being an adult is it means that you have no obligation to seriously consider any other person's idea of what being an adult means.
I agree. The above poster is using an example for "adult" which seems ridiculously juvenile. If I spent one minute of my life figuring out how to "smooth-over" disgruntled happy-hour-non-invitees I would be inclined to beat my head against a wall on account of the absurdity.
Or perhaps you did invite them, they just couldn't make it and you don't want to rub their nose in how good a time you all had when they may already be feeling disappointed about not being able to attend? Especially in the direct aftermath of the event?
It's called social etiquette and consideration. Sometimes it's misplaced; sometimes it's unneeded. But sometimes it is required.
Humans are not machines. Human interactions do not have many hard rules.
> Either you invite them, or you own the decision not to.
Define "own the decision not to." Surely you don't mean that every time you are planning an event you must preemptively inform everyone who is not invited that they are not invited, because that's clearly ludicrous.
As a more general example, you wouldn't talk about a happy hour you were going to after work with people who weren't invited/aren't invited/you wouldn't invite. I believe every sitcom on the planet has at least one episode with this lesson in it.