I just dropped my AC membership in favor my AMEX Platinum card which gives access to the AC lounges, but it's made me wonder about the policy with drink chits. In the past (with my AC membership) I would rarely get chits when I checked in.

With my AMEX, its spotty. At ORD last week, I got two. JFK the week before, one. LAX twice this week, none. Is there an official policy with drink chits? Or is it as haphazard as it seems?