Hm, I don’t know which biographies you’re referring to, but for me, a big shift came when I stopped reading for the lessons and started reading for the story.
Fiction, non-fiction, in the end, it all depends on what your filter is. What glasses you’re wearing when you read. If I’m only there to take notes and extract, yes, that’s often a waste of time. But if I go in like a dry sponge and just absorb whatever strikes me, I never regret that time spent reading.
Then again, I already consider myself rather content, so who’s to say which follows what?