A lot of people do it because it is a comfort issue. It looks like a cig, it works similar to a cig, and they can carry it around like a cig. It helps them keep there rituals while reducing the harm to their body.
Exactly. Muscle memory. A powerful thing.
As for Ms. McCarthy and her "doctor," I have no additional comments--I agree with Buggainok and Morpheus 100%.
What a bloody shame...