In practice I’ve never had a problem with running any server on my home connection except an SMTP server which required me to ask them to open the port directly

In practice I’ve never had a problem with running any server on my home connection except an SMTP server which required me to ask them to open the port directly (and they did). Most ISPs don’t seem to care if you’re not using a ridiculous amount of bandwidth. Many will sell you a package that explicitly allows it. I currently have access to live view and recorded video from my security system and haven’t had any problems at all. In the case of wide adoption of such a thing I imagine the ISPs either offering a more expensive package, or clamping down and offering their own version of the service through some monstrosity of a modem/router. It’s probably the latter that motivates most of these companies to use “the cloud”. There’s certainly ways around the problem for a motivated company, though.