Why is vanity the devils favourite sin?

 As, Al Pacino most famously said "Vanity, definitely my favourite sin!" have some of you asked yourselves why? Or is it just me! With the rise in personal training, cosmetic surgery is the new drug of the masses, Vanity? What does it mean to be vain? Why are so many people now getting cosmetic surgery? Why are men now getting hair cuts every week and why do men now wear handbags? If you think about it would it be better to be a person in love with themselves, or be addicted to drugs? Maybe people are in love with themselves and also addicted to drugs but what would be better? For some reason when I think of the statement Pacino made, another famous quote comes to mind! This quote came from the film, Pulp Fiction. "The greatest trick the devil ever pulled was to convince the world he didn't exist". Now I am not sure if Tarantino came up with that part of the script by himself but the idea did not start with him. This is from the book by Pastor William Ramsey, Spiritualism, a Satanic delusion and a sign of the times. 

"One of the most striking proofs of the personal existence of Satan, which our times afford us, is found in the fact, that he has so influenced the minds of multitudes in reference to his existence and doings, as to make them believe that he does not exist; and that the hosts of Demons or Evil Spirits, over whom Satan presides as Prince, are only the phantasms of the brain, some hallucination of mind. Could we have a stronger proof of the existence of a mind so mighty as to produce such results?"

The Fallan Angel - By Alexandre Cabanel