[PersonalOps]

Because the alternative is to embed a TLS private key that would allow you to MITM every other one of those devices. Someone extracted it? Looks like you have to either (a) bury your head in the sand or (b) rollout an expensive recall to change certs on those devices.

Why use slightly compromised HTTPS versus plaintext HTTP? Same reason they have those super cheap locks on diaries from the 90s: it's a deterrent. Makes it a little harder to do a bad thing.

[stefan_]

You have already answered why no one in their right mind would embed a shared certificate across all devices. I don't think you are being realistic with yourself when you believe people use self-signed certificates; they don't.

You are missing what happens instead. There is just simply no web management interface on the device anymore. You need to download the vendors app to configure and use the device. Maybe, if the vendor cares, they use their own CA to secure a local connection to the device. Much more likely, the app and device exclusively talk to their cloud and use that as a middleman to exchange information.

[andrewnicolalde]

But it also makes it a little harder for the user to do what they want too because they have to click through a (correctly) scary-looking security warning.