DISCLAIMER: I work for Ava Security
I agree with you to a degree, but I think perspective with regard to the intent of the hardware to lock in customers isn't necessarily accurate. For a company like Verkada / Meraki / Rhombus, the cameras (a major portion of the solution investment) become unusable if the subscription stops for whatever reason.
That said, controlling the hardware is often necessary in order to provide the more advanced feature set not typically found in appliance based cloud solutions, i.e. AI based intelligence, secure connection to the cloud service, etc.
The key here is not whether proprietary hardware is necessary...it's what kind of options are provided to the customer IF the subscription stops. For instance, Ava requires the use of our own cameras if one wants a direct camera-to-cloud offering. A key difference in our approach, though, is that all our cameras are also being updated this year (new and existing units) to be ONVIF compatible so that if the customer decides to end the service, the cameras are still usable on any ONVIF compatible platform, of which there are many to choose from. No one is "locked in" or trapped even though it is a cloud subscription model.
Alternatively, the Cloud Connector (appliance) architecture allows the use of 3rd party cameras (ONVIF or RTSP) and internally applies all the AI / analytics to those video streams.
Ultimately, the question is not whether or not specific / "proprietary" cameras are required for the direct-to-cloud service, but whether the manufacturer is willing to give customers the option of using those cameras on another platform if they decide to terminate the service.