Pool report from today's Rose Garden event (referred to yesterday in the briefing room variously as the "Beer Blast", "Beer Fest" by colleagues, to be gently chided by Gibbs that the event was a more serious one than that) notes that, unexpectedly, Biden was also present.
The thinking here, I believe was 1) to balance a focus of 2 men, actively engaged, and one President--e.g. to provide balance, and round off the numbers should the two become overactively engaged; and 2) To let Joe's loquaciousness take some of the steam and punch out of any arguments that could arise, draining it off with words, words, words, and deflecting some of the focus off of Obama, a key role for Biden since the start.
Pool report notes that POTUS drank Bud Light--popular and unobjectionable; VPOTUS: Bucklers--need we say, a "near beer"; Gates: Sam Adams, a quality home brew, and Crowley: Blue Moon, which we might note is meant to appear different and a rarer brew, but is actually owned by Coors--although they don't like to advertise this.