What would you do with it? Side load apps? The games in the app store are presumably the reason 99% of people buy it.

On android - yes.

Specifically I would sideload fdroid, and then install (free) apps from there since it doesn't need a login.

Or maybe I'd (say, on windows) "sideload" steam, and install apps from there instead of from Oculus.

The idea that the only place I can get apps from is the "official" appstore is ridiculous.

This wouldn't change if it were a store account instead of a device account. Most people use google's play store but this doesn't mean every android device needs a mandatory google account.

Also MacOS and Windows have “App Stores” that you certainly don’t need to be logged into.

The MacOS "App Store" (as in the thing they call the app store, rather than all the other ways you can pay for and install apps) does require you to login. Worse, they block updating the non-os software that came with your computer with logging into that app store.