If you have a large suitcase or other parcel it may be unwieldy to walk around Tokyo or another city with it. Subways only allow one suitcase of a certain size, so you might have to take a much more expensive taxi.
Instead you can go to a desk at the airport and have your luggage delivered same day or next day to ~any hotel, subway station, or convenience store. It will be insured and kept safe for you there to pick up. And at the end of your trip, you can send it back. The price for this convenience? Around $10.
This is not only a good demonstration of Japanese trust and customer service, it's also a legitimately hard logistics problem. I daresay that such a business could not succeed in the US both because of our defensiveness and sprawling cities.
There's definitely a huge difference in service work ethic in Japan, which probably leads to those reliability stats. I don't even know if I consider it a good or bad thing, because it's super-nice when you're relying on them there, but I can also tell that waiting on people hand and foot wears on people's mental health, and it often shows across that country.
Wow that is fantastic. I'm surprised no one "imported" that one to the states in "make everything a start-up!" days early-mid 2010s.
As a tip, it's not quite as convenient but most hotels will let you check a bag with them, even if you're not a guest. I've done that at different conferences (usually 1st day and/or last day) when I had a day left, didn't want to haul my bag, but couldn't go to from my hotel. I think I got turned down once and it was simply because they were full.