Queuing is one way that companies create the perception of scarcity, this leads to people being willing to pay more or buy without comparing the price, due to their fear of missing out. It can also add an air of exclusivity, where people will pay more for an item to convey a VIP status. I’m certain they choose not to scale the servers, the few lost customers wouldn’t be worth the cost when they’re able to price gouge the patient. And once all the stores are doing it, what choice is there?