Convenience. Some people don't desire it, and that's fine.
My wife said the same thing as you at first, and originally had no desire for any of it.
Instead of buying dimmer switches to replace the on/off wall switches, I got dimmers that go in the gang box behind the existing switches. I did this for her, because she preferred a real switch and now we can on/off with a real switch (as it worked originally) or control brightness/on/off with voice, app, or zigbee remotes.
Since I did this on all our wall switches, my wife went from using the real switches 100% of the time to now around 0-5% of the time. When we're away from home she always makes a comment on how annoying it is to NOT have it.
Asking for a brightness change while watching a movie or cooking with dirty hands, automatically tuning the lights to something warmer at night and brighter during the day, forgot to turn something off and you're already in bed, automatically turn on the lights inside the front door when we open it with an arm full of stuff, having energy monitoring, virtual 3-way switches without any re-wiring, adding additional lights to switches that don't have real switches, controlling the TV without a remote, the list goes on.
If the reliability of it all wasn't 99%+, I wouldn't want it. I keep it because everything "just works".
I could make all this computer controlled over a home server if I wanted to, but what's the point?