Of course going to a large social gathering will exponentially increase your risk of infection, but the absolute odds of anything seriously bad happening to fully vaccinated people is very, very low.

But this is my point - I don't disagree with that, but the chances of actually getting infected (despite vaccination) are pretty decent if you attend an event like that (especially if it's enclosed). The point isn't that *you* will suffer personally from going to these events, it's that you risk infecting others who might because of the possibility of becoming infectious between tests. And even if that risk is low, the consequences can be so severe that caution is reasonable.