Wouldn't it be better if they were just automatically dimmer at night? Wouldn't you still prefer a real dimmer switch, even if it moves automatically on a schedule? I can't see wanting to pull out a phone (which I may not even have with me at night) to dim the lights while my hands are wet. I don't even have a smartphone, and my flatmate broke hers irreparably the other day and has been without while waiting for a replacement.
I really don't see any reason why people should be expected to control devices which are right in front of them with something in their pocket.
There's a reason we still carry cash: when the lights go out, and the ink on the credit card recorder runs dry, you can still pay for things. People who do not carry cash deserve a nomination for the Darwin Award.
As far as I know, those things run on a schedule most of the time but maybe you want to leave early and turn off all the lights at once. Or if you want to pull an all nighter and want normal light so you don't get sleepy quicker.
There are a lot of cases when you want to change your schedule and your phone helps you do that.
Furthermore, you will be controlling the lights less with an app and more with your voice. For instance, if you tell Siri good night (and you have home kit enabled), Siri should dim or turn of the lights. Combined with Amazon's Echo, this can really be handy (although I have a lot of privacy concerns regarding Echo).
Of course it's better if things just do what you want them to automatically, and that's entirely possible with current connected bulbs. I've got some with physical buttons to control the lights, and some smarts (so that I can hit the same button for full brightness at some times, a nice evening dimmed at others, and really low level at night).
The issue at the moment is that it's not really accessible to everyday users, I had to interact directly with the system's slightly obtuse API to do that. Your everyday user just gets switches to activate a particular scene.
I agree that only being able to control stuff using your smartphone is dumb, but that's a separate question from whether IoT is useful or not, as you could have both.
I really don't see any reason why people should be expected to control devices which are right in front of them with something in their pocket.
There's a reason we still carry cash: when the lights go out, and the ink on the credit card recorder runs dry, you can still pay for things. People who do not carry cash deserve a nomination for the Darwin Award.