I was going through the earlier parts of this thread and had some thoughts....
I think you (
@PaulL ) hit the bullseye there and it doesn't just apply to the software/electronics discipline. I think it is the contrast from what the day job is, usually in front of a glowing screen or in a meeting room vs. hands on creating something tangible & useful, sometimes even using skills of the day job. Putting the creative side together with the hands on is satisfying/relaxing after a day's work!
In my case the machine tools are yak shaving for the end product which has been race cars, airplanes, motorcycles or just fixing things (better than new) after they break. My day job has been Mechanical Engineer on things like military ocean sensing/automotive electronics/hand held electronics/food service equipment/oil patch slip rings etc. etc. etc.
From young, I always had the interest in making things which probably led me in the direction of the day job. Growing up I always had the influence from people doing hands on things so it was natural.
/<ramble>
D