2022 and they still have to take the store down to add new devices 🙈
2022 and they still have to co-ordinate a multinational/multi time-zone launch online
and across a massive bricks&mortar store network, where most of the staff will be learning about the new products just this morning. The hype doesn't hurt, but it probably also helps reduce the number of online orders for superseded items they have to cancel/change, and - especially - ensures that they aren't at home to Mr Cockup when it comes to updating the sites around the world.
Imagine the chaos if the UK site accidentally started listing the new models at 9am UK time, and the US woke up to massive leaks... or if the Canadian site accidentally listed a new MacBook Air at $99.99 and was subsequently bombed with orders. Etc. Yeah, hot updates are entirely possible - and
essential if you're, say, Amazon - but when you have a relatively small catalogue and you're only doing these major updates once a quarter there's something to be said for taking the site down, measuring twice and cutting once. Also, I guess they have to fire up a lot of back-up servers to cope with the spike in orders when the site re-opens (it's traditional in the tech industry for servers to be overwhelmed and the site to go down on such occasions - Apple have a pretty good track record of not letting that happen).
There's not many product launches that gather the same level of worldwide attention as Apple, who also tend to have stuff available for, at least, pre-order in multiple countries at launch or shortly thereafter. So yeah, let's armchair quarterback them about taking the site down,