It’s really simple. You have bought a printer with proprietary parts and eco system… BBL can do what they like, eg subscriptions or enforcing use of Bamboo connect. They don’t have to justify anything, to anybody, apart from of course shareholders and investors.
Looks to me like BBL are being more than generous to users, not mandating firmware update to accommodate print farms etc, etc. They undoubtedly developed and produced a very fine product, crediting the open-source community that paved the way, raising the whole game for the consumer printer markets and likely have an ROI based on their very healthy sales. They allow third party filaments + software, with no paid subscription model, and have stated no plans to change that.
Enjoy it while you can, or they are bought-out & licensed by Stratasys or similar, who would then try to extract every last cent.