Having worked a variety of jobs, I can add that labor work typically involves a lot of standing, and some repetitive motion – but in most cases this isn't really effective exercise. Sure, you can stand for eight hours straight, which certainly burns some calories, but it's hardly a proper workout.
Just the same, it's tiring. When you get home after that, you don't want to lift weights or run, you just want to sit on your butt and watch TV or read a book. Maybe drink a few beers to help relax the sore feet and aching back.
Whereas if you've been sitting all day staring at a screen, your mind is tired but your body is ready for some activity. When I was doing work of that kind, once I got home I had no trouble making myself spend an hour at the weightbench, or running a few miles around my neighborhood.
How much bearing this actually has on the OP's question, I don't know. Just a little personal experience.
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"We are fast approaching the stage of the ultimate inversion: the stage where the government is free to do anything it pleases, while the citizens may act only by permission – which is the stage of the darkest periods of human history, the stage of rule by brute force." – Ayn Rand