Re: Dean + open (before the Incident with Gabe)
Lucifer wasn't drinking either. He could have been, but he rather felt that someone needed to be on the same wavelength as Dean, and since he'd been the person to clear this house of alcohol the last time, he rather felt it was nearly his duty.
In a way, he felt responsible for Dean the same way he did about Samandriel. So when he stepped near Dean, he made sure their shoulders touched, calling attention to himself and away from the kitchen. "Most would have still shown up if you'd made it a dry party, you know." There was no point in avoiding the topic -- and really, he just wasn't that sort. It was more a Castiel thing to avoid issues.