Their core pieces are all still very much in their prime and led by the best player in the league. I think people see how close they were to beating Boston without Middleton last year and realize they would have been in the Finals with a healthy team and could have given the Warriors a better fight.
Now you could also pick the Warriors as title favorites, but I think they have bigger health questions and aging questions, so not as safe of a pick.
If I could guarantee a healthy season, the Clippers would be my title favorites.