You like guys who are cool.  And not cool in that fake, dicky way, but actually cool.  He's so cool that they couldn't find any actor to adequately portray him, so they decided to just leave him out of the movies rather than risk not doing justice to his coolness.  He's like the Chuck Norris of Harry Potter: plain freaking awesome.  When Voldemort says "You-Know-Who", he's talking about Bill Weasley.