We forget that the dumb teenager who snuck off into the woods to drink or have sex has parents and maybe siblings back home wondering where they are. Sometimes we see this, like in the 2009 Friday the 13th. The whole story is about a young man trying to find his missing sister. All too often, however, the victims are victims and they are lucky to even get a last name.
Good writers know all of this. They know about the parents back home, the falling grades, the boyfriends and girlfriends who never make it to the page or the screen. It's the viewers and readers who forget. Maybe it's not their fault and the blame can rest with writers who didn't develop their characters enough to care about their lives beyond the story. That's a fair and valid point.
Granted, not every character needs a complete birth-to-story background. The reasoning for that is that it makes these throw away characters easier to kill in all the ways writers and filmmakers can think of. It's simpler to not think of them as complete people. Which is exactly why I am thinking about this.
Truth time: I stopped watching "The Walking Dead" during season three. I lost interest and had to choose my TV time carefully. I still follow the news about the show, so I know people are upset about Glenn possibly being dead. This upsets people because Glenn is a fully realized character whom viewers have come to know and like. But then they forget: in this show, eventually everyone has to die. The early seasons were like. Any one could die at any moment. As the show progressed, the likelihood of core characters biting the dust diminished when it should have risen. Glenn's likely death makes the show dangerous again. The despair comes down to losing someone who feels more like a friend than a cardboard TV character.
Wes Craven was one of the few horror filmmakers, I believe, who knew how to tug on these strings for greatest effect. Whether you like the film or not, his Last House on the Left used the family dynamic for its horror. When the Collingwoods learn of their daughter Mari's murder at the hands of their emergency house guests, they go nuts and dispense some crude justice of their own. If Krug and company had ended up at any other house, we'd have a different and less effective story. Craven would often use family connections to tell his stories: The Hill Have Eyes, The People Under the Stairs, Wes Craven's New Nightmare, and Scream all take into consideration the ramifications of violence done to one family member on the rest of the family.
This is also why Stephen King remains a top flight writer and one who can toe the line of sentimentality without (too often) going over it. Even the loneliest of his characters knows somebody. Dud Rogers, the dump custodian who had no one, still had desires for human contact. Using the innate humanity of even the lowest of humans brings the reader closer to that character. If we don't care about Dud as a person, we won't care about what happens to him when the vampires come.
Sure, it's safer for all those teenagers, unwitting security guards, convenience store clerks, and best friends of the week to be nothing more than cannon (machete) fodder. But when did horror become safe? Horror should be the least safe genre of them all. Far too often we return to a status quo at the end of a story and let people leave the theater not worried that someone might be following them. The world is dangerous enough.
But the job (my job when I write fiction) is to lull you into a comfort zone and then steal that comfort away. What better way than to make characters as real as possible, make you love them, like them, care for them, and then ...
And then do the worst.