Correct me if I’m wrong, but I was told that AA is governed the same way as juniors, rather than Zone league.
ie juniors, all age, o35s all sit under the same banner. Whereas zone league is a different category.

My personal experience has seen this as one reason for the lack of exposure to zl options.

Half the clubs are run the same way across all teams, inclusive of AA, so the change to ZL requires a new approach, and often new volunteers to handle the increased workload.
I think a good number of clubs are run with the ‘seniors vs juniors’ approach where it’s conflicting parties, under the same roof, playing different rules, trying to reach common ground. And there are more than enough horror stories to keep these ‘junior’ clubs from wanting to make the step up to Zone league.