The only reason this would need a subscription is to pay for the sim.
Stuff like Adobe Creative Cloud has some cloud features that lock you into their ecosystem. Not taking them up on it and storing locally is still an option (for now anyway) but you can't choose not to pay for their cloud features if all you need is their editing software.
That shift enabled this.
Not as full featured as grandparent comment’s use case (can’t start it in the garage) but it’s like 90% of the way there with a fraction of the complexity.
Of course that's just a pipe dream, because such systems are not lucrative.
It's also why nobody makes a slick, reliable, modern NVR that supports ONVIF cameras.
Ecosystems are toxic dark pattern garbage.