Areas used to be automatically imported from Wikidata based on certain criteria. However, this in turn led to some editors making bad edits on Wikidata to trigger it getting imported to MB, so we moved away from this.
As @mfmeulenbelt says, the procedure right now is to request an Area when you need it. @drsaunde is our main “Location Editor” and often responds to new AREQ tickets in less than 24 hours. It is not the plan that this is how we will handle Areas permanently, but until we figure out/agree on how to get back to automate things, this will probably be how it is.
Also note that MusicBrainz is about music. Our intent is not to be a comprehensive database of Area related metadata, for that we frequently link Areas to both GeoNames and Wikidata so that data consumers can use either (or both) of those to get more information about the Area.