Yes. That's why it's called the Internet of things. Every "smart", wifi connected, device you have uses that connection to communicate with a remote server. The app on your phone does the same to control the light.

Check out Zigbee for an example local control.

Many "smart" devices are sold with the idea that you can control your home from somewhere else. Maybe change the temperature on your way home or get notified when someone rings your doorbell. All this stuff requires servers to work.

Controlling some lightbulbs via bluetooth/wifi would be possible of course, but probably not very interesting for many.

https://github.com/jkbenaim/hs100 if you have tplink kasa hardware this cli tool lets you send direct commands via Wifi, no hub required. it is not that the tech actually needs a server, it is that the server handles IP address changes, records data, checks switch on/off status, scheduling, etc, to provide a better experience than hitting an on off command.

Pretty much, yes.

I think you're underestimating the computing power of these devices. If it has WiFi, it has an operating system.

You're looking for something like ESPhome maybe. It's a project from the same people that do home assistant. There's a web server (and/or local API) available that allows you to toggle outputs locally, your browser directly to the microcontroller.

It's crazy, given that all these devices have something powerful like an esp32, isn't it?

I've done some of my home stuff this way, but I had to program it myself. Tasmota has some features which can be used without a server, but that's just for simple stuff like switches. For whatever reason (simplicity for non tech people?), out of the box products don't work this way.

If you don't have days of spare time, you buy ready made products and set them up in minutes in Home Assistant

The computing as to when they need switching on and off is done by the computer.

I used to use Tasker and Smart Life connected through Google to control my lights. It worked but it was fucking shit. I wrote all the logic for it based off my phone, so it kinda worked for me, and everyone else in the house hated it.

Now it's all controlled by a computer based in the home, based on sensors that are in the home from all kinds of manufacturers using different protocols (because that's what Home Assistant does, conglomerate protocols) it works much better for everyone involved.

You can try to make iot devices work without a computer or cloud if you like but it will just be absolutely garbage.

Good luck