For me, the utility is in being able to turn a bunch of lights on and off at the same time. We have a number of lamps, or light strings or what have you, rather than one or two big lights. Put them all in Home Assistant and I can set all the ones I want to turn on half an hour before sunset without having to touch a button. And 99% of the time it's fine.

Equally, I can have a few lights turn on in the bedroom shortly before I go up to bed, then turn off half so there's enough light to read by, then turn off every light in the house with the press of a button. And it is a button, because I don't have a voice assistant set up.

Also, I have a bunch of temperature sensors around the house.

None of it is essential, but it's a nice quality of life upgrade for my wife and me.