Why are vampires getting younger?

the original Dracula was 400 something when he seduced Mina Harker, quite an age difference. (published 1897)

Anne Rice's Louis was just shy of 200 when he first appeared in print. (1976) (Lestat broke the cycle, being almost 250 when his book was published in 1983)

Stefan, the hero of the Vampire Diaries novels, was 500, (1991) but in the TV remake he has become just over 150. (2009)

The Civil War motif continued in True Blood/Southern Vampire Mysteries with Bill Compton. (published 2001)

Angel was turned in 1891, putting him just a tad over 100. (series premiere 1997)

Edward Cullen is 104 when he first seduces Bella Swan. (published 2005)

I know that statutory rape is a big deal these days, but does the difference between 100 and 500 really matter all that much? I haven't read, well, any of the books mentioned above, except for Anne Rice's, but is there some significant to the fact that the "younger" vampires were also turned into vampires when they themselves were young? Is there a verisimilitude in this "youth" (Dracula was a fully grown man when he became a vampire, and is thus allowed to be 500) when the issue of seduction of teenage girls raises its head?

The pedophilia angle was well developed in one of the best vampire books I've read in a long time, Let the Right One In, about a child vampire (sort of like a vampire version of Lolita, but in which Lolita has the power in the relationship). I won't spoil the ending of the book, but the vampire, Eli, turns out to be at least 200, and probably older, breaking the "younger vampire" cycle.

In other news, police in Michigan recently arrested a 100 year old "vampire" trying to rob a liquor store...