Conferences are a minefield. Conflicting opinions of if a particular conference should be, is, and what qualifies as, a "professional work environment" run rampant.

When you have everyone attending because it's necessary and/or just a break from the office, they have a professional setting because people are not excited to be there. I see this in the business domain (not-tech) conferences all the time, any recreation happens completely separate from the conference.

Tech conferences get tech enthusiasts. Suddenly people actually want to be there and have fun with the other attendees. An easy example is DEFCON, people treat it like a party with talks, because for over a decade it was unambiguously a party with talks.

Problems are multiplied when people want to relax standards of professionalism on some axis but maintain it on others (or even ratchet it up beyond what people are used to in their own offices). Clearly defining socially feasible expectations of behavior and communicating that to attendees never happens, then "incidents" occur.