I feel like whatever scary movie I watch there are always kids who go out "discovering" alone. It's usually some kid between 6-12 years old, and the family is never really "normal". Instead they are either overtly happy or strangely dysfunctional.
The Overtly Happy Family
This family is introduced to us during some great family outing or maybe a family dinner. They're laughing and enjoying their time together- heads falling backwards in laughter, holding hands, skipping etc. This family loves each other SO much and likes to show the viewers just how amazing their family is. This family ends up being torn apart or at least a rift put between them by the events happening around them.
The Dysfunctional Family
These ones usually involve parents who are no longer together in some fashion, whether by divorce, a death or just a current fight. This causes some kind of anger within the child(ren) and usually ends up with acting out. The kid(s) then will be reprimanded by their parent(s) as they don't understand why their kid(s) could possibly be acting in such a terrible manner.
But regardless of the family situation, the kids are always out and about alone- no parental supervision. Maybe it's just me here, but at 7 years old my mother always knew where I was and what I was doing. Of course I was given some freedom to choose my own activities but my mother still knew where I was playing in the house or in the yard. This is where my point comes in that scary movies have terrible parents. What are these parents doing?! Why are they not supervising their kids? They're always too busy working excessively, or too consumed with their own professional and personal lives to have time to supervise their kids. This is the biggest downfall, and clearly why bad things are happening to them!
My mother, who always supervised me, never had to worry about small gremlin monsters attacking me, ghosts trying to take my soul, none of my family members went crazy and tried to kill me, I was never possessed by a demon and I never tried to kill any of my family members because I was pissed off by my being different. So I've got to think, she must've done something right. And these crazy parents in the scary movies could learn a thing or two. Just monitor and supervise your damn kids!!
In the end there is almost always some reasonable and obvious explanation for all the craziness and scariness of the film. Someone was dreaming, the house was haunted or there is some alternate universe.
Don't you just love scary movies and their logic!?