In this case, and in most interview cases, there's already been some vetting done via resume/portfolio/phone, and face to face interviews are as much about personality and team fit as they are about technical competence. Being able to demonstrate that you can think about others socially, include them in to a small ritual, and do it in a way that's memorable without coming across as too cheesy (I don't think I did) is... dare I say, a skill.
I've definitely been on the interviewer side of the table, and if someone had brought in some cookies to munch on, it would bode well. If that's the only thing they do, and they still suck during the interview, no job.
I'd done this a few times over the years, and in a couple cases never even got a followup call back. If it was because of the cookies/cake/snacks/whatever, then I'm glad I don't work at a place that's so uptight/rigid that they can't take some fun.
FWIW, I didn't take a job after that interview, but was offered one.