If a garage door manufacturer offers me a (free, local) API to fully control my door and allows me to check a box to let Amazon in, what, exactly, is the problem? Sure, I could also allow Amazon in without checking the box (assuming Amazon offers the appropriate integration and I'm willing to deal with maintaining my side of it), but it also seems okay for Amazon to pay the garage door opener company for the first-party version. Everybody wins.

Forcing the actual device owner to use a crappy cloud service is an entirely different story, but it's not required for the Amazon business model. Similarly, many video recording devices support ONVIF and have an optional paid first-party video storage. (And I imagine that quite a few commercial users demand the former -- no one who operates a concierge/security desk or a serious office building or a warehouse or an industrial site has the slightest interest in using four different first-party cloud offerings from four different vendors of their various gizmos that contain cameras. They are going to run one NVR, possibly with off-site backup, with one integrated system for viewing and analyzing the feeds. And they will pay handsomely for that, and they're paying that money to one of several established companies in the space, all of whom require at least token ONVIF or RTSP compliance, and they aren't about to kick any of that money over to the camera makers, because there is no shortage of competing camera makers.)