In a vacuum, having more features is good. But simplicity itself is a feature. Simple things don't break as often, it's easier to fix when they do, and they're more predictable, meaning it's easier to plan your life around them.
Most basic is shifting from 5000k white to 3500k white in the evening. Color scenes are nice too.
When it's hot, I put a window fan in my bedroom in the evenings. I have it plugged into a smart switch. The google routine turns it off around 2am automatically. I sometimes adjust the time depending on season.
I haven't rewired the light switches in the house because it's not that important to me, but it would be nice to be able to say "hey google, turn off all the lights" when I go out instead of running around flipping switches.
I honestly don't care if someone in China knows if my lights are on.
That was me, a few years ago. Now I love them (I use IKEA bulbs and outlets) and would hate to go back. Being about to control my lights from anywhere is just convenient. Now when I climb into bed and wonder if I’ve turned off the light in the basement (a frequent issue), I can just use my phone, not descend three flights and causing noise for others.
I like IKEA’s implementation because the cloud service for me is really Apple HomeKit, which I trust more than others.
What about someone in China using your devices as part of their botnet to DDoS someone?
That said, when I set up Home Assistant, it was not without the need for some hobbyist motivation, but it wasn't too bad. That was over a year ago, and I have only gone into it since then to add a couple extra lights and set up a Christmas mode.
As far as the 'why', I can put the light switches where I want them, and have them do exactly what I want. I don't use voice or phone control, I have physical switches, but they're just exactly where it makes sense. An example is that in my living room I have a switch remote on the coffee table that lets me turn on or off all lights in view (kitchen, hallway, living room) and two different light scenes for reading or watching TV.
To me, it's actually simpler than flipping the 5 or 6 switches I would have to otherwise.