"alert staff of long queues at checkouts"
Because without a cloudy server, there is no way some mere human could possibly be charged of supervising the floor and noticing such problems. Funny that, when I got to a supermarket and arrive at checkout with long queues and half the checkout lanes closed down, pretty soon somebody shows up to open a lane. I'm pretty sure that they don't have no Microsoft Cloud Supervisor available.
I wonder how supermarket chains have managed for the past century.