interesting. Organizing isn't free and even if it's just a casual group without an explicit code of conduct, people don't just show up for no reason. They look for other people and see who else is showing up. There is an organizer. Whether it's the venue owner, who will tell you they're not going to do a meeting because of a holiday, or a core group of regular attendees who rely on each other to show up and get a signal of whether or not there will be enough of a quorum to launch a game/discussion. Sometimes people on the outside will show up not knowing, and find out that the meeting has been canceled. It's only when the rules become too onerous and exclusionary that people decide not to join in. In a board game group, the rules are kind of reinforced through people who don't show up on time not being able to be in a game and wait. In a study group or book club it can get annoying as hell catching up the person up to speed so they don't recover something that they missed out on because of lateness.