Offline-first used to be the norm before everything started requiring an internet connection for some reason. I was using OSM data offline 15 years ago on smartphones.

The reason it moved to the internet was not that it wasn't possible to stay offline-first. If the app depends on your server, then the owner can monetise that (e.g. with subscriptions) or track the users. It is more interesting for companies than allowing the users to buy a snapshot of the maps once and never come back.

Offline-first nowadays comes from open source projects, not from companies.