Boredom.
Back when I was commuting on Caltrain (SFBay area train the runs mostly through SV), rather than doom-scrolling on my phone I tried hard to get into the habit of just mindlessly looking out the window, sometimes thinking about problems I had this day/week and how I would prevent/solve them using a tech solution.
Having a notepad and pen on my lap (electronic devices can be hard to avoid temptations) gave me the ability to jot things down. Sometimes solutions to unrelated problems can spark ideas for current ones.
For comparison, double entry accounting was surely not invented through boredom.
The man that invented it had time to spend writing books and not slaving away at work.
Your "for comparison" is same "a well off man did what they liked" as the thing you're comparing to.