Playing a high level game of Starcraft or Dota is more exhausting to me then programming. With programming I have to think of some designs, spend some times with the tooling, setting things up, to all the busy work surrounding the core problem and so on. Sure there are moments when you really have to think very hard about what you do as well, but its not constant.

I can take easy breaks. Run some tests and so on.

When playing a game you have to be totally focused for longer periods and not just focus but also execute and handle the concept of being activity opposed. Its like if you were programming and the compiler was activity being evil.