Personally? Sitting around too much makes me anxious and antsy, not to mention it makes the time go by really slowly. It’s hard to enjoy pastimes when you’re stuck somewhere you wouldn’t be if you had the choice. (Also, as others have mentioned, not everyone can do those leisure time activities while at work).

My work is actually a little abnormal, but we have plenty of days where we are mostly just waiting around doing nothing for 10hrs and then working really hard for two. Sometimes I do like those days, but more often than not, I enjoy keeping busy with work stuff because sometimes those 12hr days are even longer. If I sat around for the majority of that, I’d be bored out of my skull. Yeah, I can read/do a few things you mentioned, but not for that long.

I also sort of get to live inside my head while I’m working idly with my hands. It’s a little freeing for me mentally to take the load off of my “leisure” brain. I listen to music and kinda pass the time doing my job. And I actually like my job. So that’s a huge benefit.