They're cheap, they're almost always horror films, and they usually suck. They're Found Footage movies.
Movies. Never films.
The Found Footage boom got its start when 1999's sleeper hit The Blair Witch Project (which, for the record, is a movie I enjoy) grossed $248 million in the box office after only costing $25,000 to make. Movie studios quickly realized they could slap together these cheap cash cows in a few months every winter and brunch with Mr. Moneybags all summer long.
The reason most found footage movies stink is no mystery. They're about 90% horror films, and horror films don't need to be good to make money. Like explosions in an action movie or a shirtless Matthew McConaughey in a rom com, as long as horror movies supply a few jump scares they'll get in the black. Why spend the money on Mercedes when people are willing to drive a Honda?
Still, just because a town might not have a law requiring you to clean up after your dog doesn't mean its cool for you to leave's your dogs poops on everyone else's lawn.
Not every found footage movie has been a cynical crappy cash grab. When the genre is used as a necessity rather than as a gimick it can be endearing.
Low budget gem Chronicle is one of the best super hero movies of the last 15 years.
It's a genre that, when used correctly, is a really nice touch to a low budget film. Unfortunately, it almost never is.
Found Footage Movies: Overrated.