Well two differences... one only applies to some of those things. In the case of all of the physically active ones they to some extent self-regulate. There is really only so much power-lifting you can do in a week, and very few ways around that max (even assuming steroid use)

But I think the more relevant issue is far fewer people seem to be prone to obsession in any of those other spheres. It's not that hardcore gaming is any worse than an obsession with chess, it's that far fewer are obsessed with chess.

I found this article (which came off of hacker news in the first place) to be super relevant. http://www.paulgraham.com/addiction.html