Sex and violence are integral parts to entertainment since the idea of watching other people do things was first thought.
The ancient Romans enthusiastically watched real men, women and children be publicly raped, tortured, fight and be executed in horrific manners that would cause most people to violently puke in disgust. The first Christians to try to stop this so outraged the mob viewing the games, as they were called,that they were literally torn apart by the crowd.
In modern times we have mostly replaced actual human suffering with special effects and computer graphics, Ala the Hostile films and God of War games for example, but the news media has operated for many decades if not centuries with the old adage "If it bleeds it leads".
Imagine this, a scientist creates a cure to a terrible disease and saves thousands, maybe he or she gets coverage at the press conference announcing the cure from many respectable news organizations but will that be that nights leading story. Doubtful, now imagine that same scientist goes to work with a weapon and starts killing many co-workers before being taken down by the police. Obviously the police will nearly be outnumbered by the media storming in to get the latest info, talking heads will try to explain the violence, helicopters will circle for hours over the crime scene and certainly the local and most national and international news agencies will lead with it. Why?
Violence sells. So does sex, look at the tabloids.
We say videogames need to grow up but do we really mean it. Are we really happier as adults with responsibilities, compromise, jobs and bills to pay than we were when we were children, free and forgiven for doing and saying what we want when we want.
Even in supposed mature industries such as film the box office clearly shows a Iron Man or Incredible Hulk with there clear, happy and emotional baggage free ending will fare better at the box office than a No Country for Old Men or The Watchmen with their lack of a clear resolution or happy ending.
There is a place for mature thoughtful videogames as there are is a place for them in film but the demands of profits and the masses fear of doubt and introspection will leave them on the fringes as they are in all media.
Entertainment is about escapism to power, glory or joy with the rare trip to fear and disillusion that so plague us in real life. Games will mature in their own time and in their own way.