Program suppliers have changed to a subscription model as people do not necessarily need the new features a new version can offer and so wouldn't upgrade (though in some cases it can seem as a downgrade).
Sage accounts are not always perfect and it can be frustrating with the lack of features and options that others provide. As a result users may wish to change to another accounting system. However, once the Sage system has been left, ex-users will no longer be able to access their own data through the Sage interface but would have to rely on exports.
As accounting records have to be kept for 6 years, a perpetual read-only (archive) licence which allows access to data already stored but allows no additions or changes (like like a company archive) would permit this required access. The program used does not need to be updated to a later version (so there are no further developmental costs to Sage) and it could only access historic data.
If data is stored on the cloud (eg Sage servers), then a reasonable charge for that is proper.