On both ends – I guess more on the 'I'm getting a drink' one because I agree that after a while there is no reason to stay sober anymore, because everyone else is on their way already. It's either that or go home, which I do frequently as well. But it very much depends on the kind of people I am with – in many cases it's not just colleagues or people I find interesting in terms of technological background: they are my actual friends (not Facebook-friends).
And despite getting smashed I've still had a lot of interesting conversations and discussions with people in the same setting. I don't want to call anyone out which is why I won't name names, but I think all (three) conferences I attended last year had an "open bar" at some point and it was still worth while.
One was an amazing weekend of great talks, conversations, food and drinks.
And I don't regret going to any of these either. For starters, I can stop whenever I want and go back to my hotel or go home. I can still stay around and not drink anything and chat with others all night if I want to. Or do the opposite and have a drink with them.
I personally caught myself pondering about how you keep a level of professionalism – e.g. when you see your work mates (and/or superiors) drunk all the time, how do you keep the respect around?
We hired a lot of people in the last two years and while it's good to be friends with everyone you work with, I think there is a gray area of how far you want to go. There is work and after-work and in the end, some people manage it and others do not. For myself, I just decided to not shift into last gear when I go out with them and that means I can still have a good time and even have a drink if I want to. Got that much self-control (or maybe just fear of the next day).
I'm not sure I agree on a ban for alcohol from conferences. I can see where you're coming from and I'd like to think people should consume within reason, but I'm sure that doesn't really work out at all. At least for the majority. In the end it's always freedom of choice.
I give you that though: Maybe drinks should not be free so people don't get wasted right on. Whoever sponsors them could also sponsor something else, or something more worth while.