There's a chain of hotels (Yotel) that is known in part for its robot that will stow luggage the hotel is holding for you. In practice, the staff mostly stows your luggage like every place else because the robot doesn't have anything like the throughput you need at busy times.

The flipside to it is, during slow hours you still have the robot at the ready to help the odd guest. The robot just sitting there generates virtually no costs (bar the minuscule amount of electricity to maintain situational awareness), while at the same time freeing humans to do more important tasks. Which may very well be family and social life.

Maybe? There are always people on duty anyway and the robot contraption probably takes up way more expensive urban space than any cost savings it brings. I'd be pretty sure the robot is far more about having a hip urban vibe than any sort of ROI.

You could also just have lockers.

I'm not sure I've ever seen a hotel with lockers. Part of it is probably not wanting to become a public luggage storage facility. The other is probably that, while lockers work well for modest-sized carryons, once you get into bigger suitcases like a lot of people travel with, you can't really lift them up to a locker that's off the ground.

Lockers (or luggage storage generally outside of hotels) are, in general, pretty scarce in the US--and at least a lot of Europe in my experience. It's one of the things that makes a regular hotel pretty handy; I can drop off my luggage the day I arrive or leave and not have to restrict my activities until it's time to checkin or depart.

They're very common in hostels, particular backpacker hostels, but that fits with having limited luggage. I've seen them once or twice in the cheapest hotels.

The main railway station in a European town sometimes has luggage storage. In Germany that's usually lockers, in countries with more history of terrorism (like the UK) it's a room with a metal detector and an attendant.