(North American airline)
... everyone in the cabin is either non-rev, upgraded with miles/vouchers/YUP/QUP/KUP, or op-upped

... you only need to walk to the galley once during the flight to get service

(other airlines)
... everyone in the cabin paid for first

... you don't even need to press the call button once in flight to get great service, they just seem to know you're about to ask for something