No one actually ever got free updates forever. Support for the Jolla1 ended at some point, then for the Xperia X, etc. XA2 will probably follow soon. There is no obligation of any kind in their EULA about how long each specific device model is to be supported, the only remark is “Free updates AS LONG as the device is supported”, which means that Jolla can actually stop supporting a device whenever they decide to do so. And they do it.
Of course, so far it’s been quite many years of support per model, for which we certainly should be grateful. But if it doesn’t bring them enough money then why not simply shorten the period of free updates to e.g. some fixed period clearly stated in the EULA, like e.g. 12 months or 24 months of free updates, and then simply require payments for any (optional) consecutive updates past that guaranteed period. Instead of monthly subscription for literally nothing, because it doesn’t guarantee literally anything.