In my house, the central lights turn themselves on when it becomes too dark (except after bedtime), and off when it becomes too bright. Lights turn on automatically when someone enters a room (when it is dark) and turn off when they leave.
When the last person leaves the house, all lights go out, except when I am on vacation, in which case the lights turn themselves on and off in a pattern that looks like I am at home.
After lights come extractor fans (keeping the humidity constant) and heat/air conditioning.
It is all about maintaining a comfortable home environment without having to manually turn things on and off all the time.