The other reason is...inspiration.
I use not only books but television and movies to get my mind focused on a particular genre or topic. Book one in the Elements series that released two weeks ago focused on psychics, demons, the hunt for a killer loose in New Orleans and a prophecy. Needless to say I researched psychic phenomena, hauntings, angels and demonology. It sounds silly but I found myself looking over my shoulder many times and if a site freaked me out too much I quickly closed it! Yeah my blood ran coward’s yellow for a while there. Did it stop me? No way. I have a DVD library that continues to grow and includes titles, Ninth Gate with Johnny Depp, Constantine (Keneau Reeves), Underworld (Kate Beckinsale), and the Supernatural and Vampire Diaries series.
My current work in progress is book two in the Elements series and this story includes the topics from The Burning Seal and adds magic and vampires. I consider myself lucky to have so much fun writing this series!