By for funsies I mean someone who just likes applying rationality because thinking about certain things is fun. Like, how I study physics because physics is awesome, more than for any intended use of physics.

That seems to be the reason for why I am doing it. I suppose that believing that rationality is instrumentally useful would provide a stronger incentive to think about it seriously. But I currently don't expect formal rationality to be worth it when it comes to having success in life, at least not for me. And even if that was the case, I perceive social abilities to be much more important.