I have tried to have technical conversations at parties and in bars with people I know to be interested in and knowledgeable in the topic. It's basically impossible.
Firstly, the loud music and other conversation makes it very hard to hear what they're saying, and the things said therefore tend to be simplified into what can be said simply in short words.
Secondly, they are often drunk and/or more interested in talking about beer or something than the topic they presumably are at the conference to advance. This is, of course, understandable; they're not expecting to have anything whatsoever to do with the conference topic at the party, since nobody else is, either.
Thirdly, there are no whiteboards to use as discussion aids. It's also quite dark, and it's often cramped so you can't easily show somebody something by moving around. Basically, bars and party rooms are not exactly conducive to productive discussions. (In the past there would also be no internet and, further back, no computers, but that has thankfully become a non-issue these days.)