• I am sure you have at least a couple of instances in a week where you go "damn, I forgot to switch the lights".
• You are tired on your sofa and wanna watch a movie but the lights are too bright.
• You want to simulate someone is home so you don't get robbed.
• meeting mode: warning them with a red bulb in the living room, and lowering the TVs volume all in just a click, while ensuring that your robot vacuum stops cleaning and resumes later.
• get a warning that your room's humidity level is high, and directly offering a button for launching AC.

All those things I have not done, yet. I don't even have the Zigbee dongle. But surely through the following months and years I will find little things that I could do that sum up to a lot of comfort and saving time.

Also, relay switches and sensors are so cheap it can simply be a fun hobby.