Storing data locally makes the experience faster since there's no waiting for a server to load.

Privacy-wise, because there are no identities and no accounts, a user can choose to change their name and address anytime and there's no connection. For example, to a different PO Box with a different name. I would have no idea that 2 orders belong to the same person.

So it's just as much an experience thing as a privacy thing...the privacy benefit came for free.