I think this cop-out epidemic can be explained by the fact that horror is the toughest genre to do right. No other genre demands as much energy from its viewers, and the measures a story must take to extract such energy are great. Consider the emotions called up by other genres: the excitement of a trip, the romance of a date, a good laugh with friends, periods of sadness or introspection.... real life circumstances can make those moods peak for several minutes or more. But the high intensity panic which horror films aim to cultivate is, in real life instances, only momentary. Sustaining that emotion for the better part of 90 minutes is a herculean task -- no wonder filmmakers shy away from it!
Naturally, panic needn't be sustained continually for the duration of a film; it's enough for scares to crop up at intervals in a background of unease. But even that goal poses logistical problems. When we encounter a lethal threat in real life, one of three things quickly happens: we evade it (and then stay clear away!), we succumb to it, or we become accustomed to it. The horror-monger's challenge is to deny his principal character all three of those options for the story's duration, without losing credibility. Tough task! Let me sketch the major horns of this multi-lemma:
*The victim must encounter the threat repeatedly throughout the story, BUT a victim stupid enough to voluntarily remain anywhere near the threat after the first encounter will lose our sympathy. (Pat solution: limit victim's mobility [car won't start, snowed in, crippled].)
*The threat must remain threatening in the minds of the audience, BUT the primary victim must survive repeated encounters with the threat, which will endanger the threat's notoriety. (Pat solution: let the threat kill off secondary characters during each encounter, saving face without killing the primary victim too soon.)
*Our knowledge of the threat must increase throughout the story, since finitude and stasis breed calm in the viewer, BUT the threat must remain mysterious, since comprehension and certainty also breed calm. (Pat solution: the threat is gradually revealed to be one thing and then turns out to be something else, rebooting the mystery.)
*Encounters with the threat must be brief to avoid exhausting the audience, BUT how can the victim escape from the threat temporarily without escaping permanently? (Pat solutions: the threat is 'toying' with the victim, the threat has minor but decisive weaknesses [garlic, silver, sunlight...].)
I'd like to expand on the first clause of that last point. It's important not to scare the audience for too long, or revolt them too much, or they'll tire and abandon the story. They may take their emotional leave in good humor, laughing with an outsider's smirk at the characters' screams, or they may fold their arms in disgust, but in either case they'll part company with the horror, viewing it now from outside the noose. Good horror disturbs us with enough restraint that we remain sensitive to it without looking away, allowing us to immerse ourselves in subjects that are otherwise too painful to dwell on.
Comedy serves a similar purpose, but I think horror cuts closest to the bone. A shame that today's filmmakers approach the genre half-heartedly.