I don't consider ... eating ... free time, I consider them maintenance :)

If I mostly lived on Soylent or Mealsquares you'd have a point. Given that I often-ish go out to restaurants...

Anyways my point is that most of the things you listed are definitely work for the brain, yet people don't think they affect your ability to be productive at work, since they're not something you're paid to do, which I don't think makes much sense.

Well, not all the things on that list are the same: arguing that someone is wrong on the internet may drain my stamina almost as much as my paid job, but chatting over a beer occasionally glancing at the TV will drain my stamina almost as little as idly daydreaming -- possibly even less, depending on what I'm daydreaming about.