That might be the reason I never noticed something like that, I tend to raid the Hotel Bar in the evenings and last time I stayed at Olive8 I was the only one (known to me attending PASS) doing the good ole "maximize your cocktail input in the shortest time" before heading to sleep (which I will do again next time, sometimes you have to push the Garbage Collector Button yourself). During our local Chapter evening out I haven't noticed anything like that either. I didn't stay too long that evening when we went to the Gaming Center (which was asides the Welcome Cocktail thingy the only thing I remember back then being organized for all attendees) so I can't judge that. Actually, not sure if the "Networking" Meeting took place outside the Conference Center but I think not, it was just late in the evening.
So maybe someone's ignorance might be partly because some events aren't even that well communicated (or might be something I simply am not aware of PASS is doing these days) or he / she doesn't see this as paid holidays and prefers / has to do other stuff in the evening. And yes it's sad and in the case(s) you encountered definitely needed, though I agree that better behavior should be enforced. The question is how? Ban booze and have everyone give a sample of blood on a daily basis and those that fail have to leave? I would consider that booze is the main point in some of this behavior but I'm not sure how to tackle this. If it's a PASS organized evening out in the city you might ask everyone to have their badges visible at all times so you could at least Name people who did wrong but once you go somewhere with what? 50 - 3000 People and do not have such requirements in place I would not be able to even track down a single person afterwards, let alone the next morning.