You're conflating efficiency norms with respect norms. Never mind that the core reason for no queues in bars is space efficiency and historical norms, allowing the bartender to select regulars, better paying customers, etc. without being stressed for time.

But in any case, your edge-cas applies when someone exists to manage the queue. That's not the case for e.g. elevators, self-checkout lanes, DMV lines, or, I'd argue, that vast majority of queues encountered regularly.