Why does Apple close its online store?

We’re taught that when we build computer systems, we need to strive for 100% uptime. Amazon going down gets reported as news. Yet one of the largest companies in the world happily takes its online store down for hours at a time. They must get ~80% uptime on the Apple Store!

Technically, there’s no reason why this situation should persist. Back when they started doing it, it was easy to point at a possible incompetence on the part of Apple’s web team. Now it’s been standard operating procedure...