Because no one can actually define what an 'actual' vampire looks like,the media creates there own variations of what they believe a vampire to look like. Ann Rice's portrayed vampires are only one variation,though the concept of vampires are similar i.e. drinking blood & hatred of the light etc,the vampires themselves vary some are the apitimy of evilness others are these creatures that have a strong influence over there surroundings etc. Rogue Jedi said Anne Rices Vampires cannot do a sereis of tasks humans take for granted well if you look at Joss Wheddons Buffy/Angel Vampires they can do all three as can John Carpenters portrayed vampires. Some directors/authors like Bram Stoker and Francis Ford Coppela tend to take the more traditonal view on Vampires i.e. Hatred of Religous artefacts,hatred of sunlight,blood suckers the thing that most people assocaite with the tradtional vampire concept but to a new generation of directors and authors such as Joss Wheddon,Patrick Lussier and indeed John Carpenter Vampires are portrayed more 'hip and trendy' who do not sleep in coffins and wear black cloaks but walk and act like any normal 'living human' Patrick Lussier took the extra steps and created a whole new scenrio to the orgins of Dracula - The most famous of all vampires.
There IS actually a vampire deseas. A real thing. They have to drinck blood, or else there face and skin will "dislockate" and look like a muffine almost, three skin is EXTREAMLY sesnstive to the sun, blood heals that, There Canins tend to be longer and pointed, And also, but in VERY rare cases, there bones are fluo pink or green.
It is with such a case that started all the vampire stories. (in my opinion) I mean, look, a guy, goes only in the night, long canins and kills people to get blood. (i suppose it is like "i feel like drinking orange juice" or somehting). It is also a herediairy deseas.