hey why are the Van Helsings always the Vampire Hunting Family in modern Dracula stories. Abraham Van Helsing might be the guy who knows stuff but his family is off in the Netherlands and/or dead and totally uninvolved in the plot. Abraham's great-great grandson has no reason to be doing backflips and chopping off heads or whatever
You know who is a family who hates Dracula so so much and would totally teach their kids how to hunt vampires? The Harkers. Give me a modern vampire story where the protagonists are about to die when out pops Quincey Arthur John Lucy Abraham Murray Harker the Fifth, armed with a giant knife and an encyclopedic knowledge of train schedules
I think it's a combination of the fact that Van Helsing is a really cool name combined with him being the one to kill Dracula in both Universal Studios' 1931 movie with Bela Lugosi, and Hammer's Horror of Dracula. The Hammer film was probably the first time he was portrayed as a professional vampire hunter.