Think about the medical system, people hate to be put onto waiting lists (queues), but empty queues means that extremely expensive resources (operating theatres

Think about the medical system, people hate to be put onto waiting lists (queues), but empty queues means that extremely expensive resources (operating theatres, staff, surgeons) are sitting idle which is very inefficient. Ideally queues mean that another patient is always there when the operating theatre becomes idle. Because medical need is not smooth and constant sometimes they fill up, sometimes they drain - they allow planners to match average need to resources. So non-empty queues are a good thing, even for hospital waiting lists. (To forestall arguments, of course the operating theatre example is not a pure queue example, some patients get put to the head of the queue according to triage - for the purpose of this example it doesn't matter)