I ask the same question about checkouts in supermarkets, although at least there they will make some effort to open one if the lines at the already-open ones become too long.
This morning at Medicare, I was in a queue of at least ten people. Old people, women with small children, heavily pregnant woman (me). And four unoccupied customer service points. Which remained steadfastly unopened.
Is it just to create an illusion that fast and efficient processing of customer's claims might be able to happen in some utopian world?