>I used to ask this question, but now I've generalized it to asking if someone has any hobbies.

I think this is far better than "pet projects". Some people would rather socialize, read literature, play music, play or watch sports, work on cars/home improvement, paint, travel, camp, write, get involved in politics, read the news, or any number of things! Rest and relaxation are particularly helpful to mental health. Even playing video games, watching movies (with a certain amount of moderation), or doing things that are more classically endorphin-releasing "fun" than programming contribute to a well-balanced individual.

I'd rather hire someone with a sense of balance in their life.