Thank you for the answer above, but I'm still not convinced of the benefits? I do not want anything 'automatic' in my life. There are too many reasons to not do things automatically. Having something happen just because I do something else is programming myself into a robot, in my eyes. I'm much less predictable than that and so is my life as well as others around me. I may walk out the door, but I may also be coming right back in, in your example. Or, someone else is home/etc. To each his/her own though!
Thanks again for the details. 'Home Automation' is not something I will be using soon (if ever).
Doesn't always have to be used for home automation, can be used for other things let collecting temperatures from all around your house in one convenient spot. Watch the video you might be surprised what you think you can use it for. He explains how his house works in the start but the explanation of MQTT / OpenHAB starts around 16 minutes.