Some real people can't communicate. Reality takes a very circuitous route to get from A to B, but a screenplay stays on course. Movies aren't reality, but movies are about reality. Movies tell us something about life and if they are too divorced from reality, they are make believe, telling us nothing. I believe writers have the responsibility to inform with accurate information, and to avoid misinforming.
Sex is another area where reality is an uneasy portrayal.
Movies are constantly pushing the acceptable limits on things like nudity. This is largely the director's domain, but the writer provides the basic scenes. Being on the edge is titillating to many viewers. In an age where soft porn movies are commonly available, standard movies and TV still find it necessary to push the limits to compete. Today the majority of both men and women spot the tush first.