Maybe people want disabled sims because they themselves are disabled and don't think of their lives as being a pity party. A wheelchair is not a limitation of who you are, nor does it have to be depressing. Maybe the most important to them isn't being able to walk but to live a life being accepted for who they are. So when they try to engage in a game of fantasy their fantasy might just be to be who they are , physical limitations and all, and live a full life. Not be told that they have to be physically able to enjoy those things.
