People love to do activities where their efforts and rewards have a strong correlation to each other. Athletics are an activity where hard work pays off. That’s rare at a job.

It’s because the product of their labor is taken from them and they are worked like animals.

Untrue, fair amount of old folks are so workbrained they keep a job after retirement as a hobby. One guy I know put in ridiculous hours because he would be at the bar otherwise.

Running a marathon, participating in a fighting competition or climbing a mountain is the reward for months or years of grinding, which isn’t necessarily fun. If you want to go with your analogy, compare running a marathon with getting paid, and training for a marathon with working.

I’m envious of people who love their job.

Like those things, you can quit work anytime, but unlike them, you sure as hell can’t wake up one day and think “Yeah, I’ll get back to that work today”