The more interesting question to me is why the robot has to go scan the shelves at the time you ask, when there could just be one (purpose-built) robot that walks the shelves once per night and builds up a model of the entire store that gets used by the other robots for the rest of the day. The hospitality robots wouldn’t even need to be able to see the shelves; they’d just need to be able to guide themselves to the right coordinates in the store and say “it should be right in front of me.”