So I am a member of a number of boardgame groups with meetups that each happen at the same place either regularly or on a different date each month. When they do happen, I just go there, and never RSVP anymore because nobody cares. In fact, one of the weekly meetups would regularly have 2-5 people RSVP but 15-25 show up. What prevents everyone without a headcount limit from doing more of that? :)