I read a lot as a child too, but it was writing that I've found has motivated me to develop more complete models of people. Whether it was my mom's detailed criticism of early stories that I wrote (included the dreaded "that's awfully implausible, sweetie"), or the fact that writing gave me incentive to go out and talk to people or try new things in order to have something to write about, that's where a lot of my motivation came from to develop better empathy.

Aside: I think a surprising number of my life decisions boil down to wanting to understand people better (whether "just because" or in order to be better at other things.) Example case: choosing to study nursing instead of physics. Despite my mother's insistence that I would be "an incredible academic", there was a part of me that always chimed in: "You're already good at school/studying/learning/etc. You're terrible at people skills. People skills are more important than study skills for writing good stories. Can you imagine how awesome your people skills would be after 10 years of being a nurse? There you are!"