But if you don't kill them they turn into a vampire and they''ll start competing with you for food. Butterfly affect says it would grow exponentially. Better to feast well and kill the victim.
..... cut them with a knife and let the blood drain. Drink it. Boom, sorted.
Extreme addicts aren't generally very forward looking.
I feel like this really only applies where obtaining said addictions are difficult to do so. Money for heroine as an example. With the power dynamic of superhuman speed, strength, and a theoretical immortality being vastly beyond that of their human prey, the foresight of a sustainable method of survival should be common pracitce.
But they also know you are a vampire now. Leave no evidence behind.
Pluscit really depends on the series. In the World of Darkness vampires are supposed to leave their victim alive because a dead bloodlessbody is evidence of the existence and location of vampires.