Not the whole story. Sometimes they do that. I find it quite fun to watch. It's interesting to see where I am in the pecking order on particular routes.

However, they often (and I believe are supposed to) go to everyone in an arbitrary order, then do the ranking part out of sight. Apart from the issue of disclosing status to everyone, there's a huge advantage to this over all the other methods: Some people don't care! If they get an "either this or that" or an "I don't mind" from some of their high-priority customers, they'll almost never disappoint anyone. If they take orders and/or start serving in status order, the decision has to be made before they know what they might run short of.