Hm, I have the opposite setup - I operate a dehumidifier. The building I live in gets humid quickly, and that causes mould quickly. My tank fills. When the tank is full (and, depending on outside conditions and number of humans present, that happens anytime between 16 and 40 hours), the device stops dehumidifying to prevent tank overflow.

Yes, I do still need to be present to empty the tank. But automated warnings when the tank is full (in combination with more intense 'room's LED lightbulb flashing red' when BOTH the tank is full AND humidity rises above 60%) are nice - otherwise, I'd have more mental load to check a little tiny LED on the device itself every two days or so, which, surprise, I would keep forgetting.

Why are outside sensors relevant in my use-case? Because running the dehumidifier is pointless when the window is open AND outside humidity exceeds inside humidity (and electricity is expensive where I live).

Secondary use-case: mould and 'rentee did not air out the humidity correctly' are some of the more common points of conflict between landlords and rentees over here. With my smart dehumidifier (and a few more sensors placed around the apartment and outside), I have a paper trail should this ever come in front of a judge that yes, in fact, I correctly fought humidity.

Is my use-case everyone's use-case? No. Am I probably over-engineering this? Sure, it's possible. Is it nice and kind to make broad paternalistic assumptions and snarky jokes on what and what not "anyone" really needs? Doubtful.

You're arguing from device capability. I’m arguing from human cognitive load and failure modes. The question isn't "can the (de)humidifier regulate humidity on its own?", but "how many low-level checks and mental reminders does it eliminate over months of use?". For people who forget, get distracted, or simply want fewer things to keep in mind, that's not dubious value - it's the entire point.