I don't get this question exactly, but when I tell people my ideas for Vampire stories that could be in the same universe as The Lost Boys, many ask "Why not just change the names and make it all original?" or something like that.
TLDR: Why Lost Boys? 'Cause they're cool.
For anyone who's interested in a deep-dive into my reasons for making a fan film, first let me tell you why I chose to crossover with this particular franchise: simply put, The Lost Boys is inarguably the most influential Vampire movie since the original Dracula. As much as I love Buffy, the show straight-up ripped off (or homaged) The Lost Boys in many ways, from the Vamp-out face, the Vampire horror/comedy blend, the teen-centric story with fashion more reflective of the current time than day gone by, and I'm not even going to get into the Spike/David comparisons, as a simple picture covers that. It's true that Buffy actually took a lot of things first done in The Lost Boys and did them better, but they had the luxury of a series to build their characters and stories, and for well... growing pains. Unless they're a completist, I advise people to start Buffy with season two, as one is very hit and miss.
Vamp-out
The Vamp-out face sort of has it's roots in the original novel, Dracula, which is the first example I can find of Vampires having two distinct looks that they switch between. However, in the novel, the two looks are reversed from what we think of today, as when Lucy is in the process of being turned, she looks radiant and healthy when she is in the mood to kill, and looks sickly and gaunt when she reverts back to her normal, sweet persona. The Lost Boys flipped this and turned it up to eleven by making the Vamp-out faces grotesque and almost Demonic. Most think of this as traditional Vampire lore now, but it only goes back to 1987.
Horror/Comedy
Warner Brothers flip-flopped between wanting a darker tone or completely family friendly, as the blend of horror and comedy in film 'til that point had usually disappointed at the box office, but Schumacher insisted he could make it work, and the final film remaining relevant and talked about 35 years since its release shows he was right.
Modern Vampires
Vampires blending in with modern teens had also never been done successfully prior to 1987. With most depictions either showing Vampires prancing about in rented formalwear or just being a bunch of basement monsters (e.g.: Salem's Lot) to highlight their separation from humanity, The Lost Boys again went the opposite direction at top speed by showing the Vampires not only blending in with modern teenagers, but being the 'cool kids.' This only makes sense; if you're going to look 19 forever, it'd be best to dress the way 19-year-olds do in each passing decade. It's kind of surprising this wasn't an established norm until '87.
With The Lost Boys so completely revolutionizing Vampire fiction, it seemed like it'd be fun to crossover our Vampire gang with that world, but our gang are not the same strain of Vampire as the Boys, so they have different weaknesses, but that is a tale for another time...