HOLLYWOOD IS making an awful lot of movies about teen-agers these days. Over the past few years there has been a flood of films about adolescents being pursued and dispatched in various gruesome ways by psychotic killers, or overcoming adversity in the cruel rituals of athletic competition and dating, or getting involved in gamy situations behind the backs of adults.

The reason is that as more and more adults and younger children stay home and watch their movies on VCRs, teen-agers, with their age-old desire to get out of the house, are becoming very important to the movie theaters. Does this mean that adults who like to go out to the movies will eventually have nothing to choose from but teen exploitation films? Probably not. As the first generation to be so heavily indulged by Hollywood, today's teen- agers will probably continue to go to movies, and we suspect that Hollywood will continue to give them films about themselves. What this means is that in about 25 years we will have a wave of middle-age exploitation movies, with plots like these:

* A man paying his bills realizes that no matter what he does, the balance on his Visa account will always be $825. He rushes to a second-story window and begins to cut his credit cards to pieces, letting the strips of plastic flutter to the sidewalk below, where a crowd of children encourages him by chanting "Snip! Snip! Snip!" He is finally talked down by a policeman with a bullhorn, who pleads, "What if you needed snow tires right away and your checking account was low?"

* A woman impetuously leaves work an hour early and goes home to have a drink, leaving the five members of her car pool stranded. There are harrowing scenes of the car poolers trying to figure out unfamiliar bus schedules or paying high taxi fares to reach their homes in the suburbs. They are all very polite about it, but take their revenge by dropping the woman a mile from her house the following Monday.

* A slightly overweight man is at a shopping mall trying to decide whether to order a second chili dog. He finally does. Later he makes a daring decision not to install an alarm system at his home, even though a neighbor's house has recently been broken into. In the climactic scene, he has lost a little weight through a good diet-and-exercise program, but has had a break-in at his house. He and his wife vow to replace their stereo system and a VCR for their teen-age children, who never go to the movies anymore because there are too many old people there.