Sex and drugs are generally not found in games, and in fact, most gamers who have no problem envisioning game violence, don't want sexuality of any sort in their game. The cathartic experience they're looking for has to do with power and conquest, slaying the dragon, winning the war, settling the Catan. If you want sex in your sub-culture, let me recommend a good comic book store. Games are about conflict resolution; the bigger the conflict, the larger the cathartic resolution. That you can do this while consuming carbonated corn based beverages and talking national politics is all the better.
The original games of old were of two types, racing games and conquest games. You raced your stone around your wooden board or your stones moved around a board and cleverly took other stones. Basic, fun, conflict resolution. Those who played these early games had leisure, and historically leisure has been a top down phenomena (so says Karl Marx). Games were originally for kings and pharaohs, then later on the rich. Only recently in history, average adults played games. It has only been in the last hundred years or so that children have begun playing games. From what I can tell, in our modern culture, they play with toys only for as long as it takes them to transition into games (traditional adult activity). So it's not that violent games are being aimed at kids, it's that culturally, kids are engaged in what has historically been an adult activity. Not only that, but turning things around, there's suspicion and ridicule for adults who spent their leisure on the activities of ancient kings. Go figure.
We could argue that kids shouldn't play games, which is a major cultural shift. We could argue that games shouldn't be so violent, something that goes back to the beginning of cultural history. Instead, increasingly, violent media in culture is getting a second look. Violent games, according to some studies, prevent violence. It's make believe, a learning process about violence, or maybe, according to one study about violent movies, if you're in the demographic to commit crime, and you're instead doing something else, you're too busy to get drunk and mug that old lady or break into a car:
Whether the effect is the result of catharsis, being "scared straight" by Hannibal Lector, or merely the consequence of sequestering a large portion of the population most likely to commit crimes during hours when a high percentage of crimes are committed, the economics professors maintain "on days with a high audience for violent movies, violent crime is lower,"Games have violence because good stories have conflict. Without conflict, you don't have that cathartic resolution. People obviously want that experience, otherwise I would by replacing my miniatures section with twenty seven versions of Sorry, a solid version of an ancient race game. Violence in games, some argue, helps people understand the consequences of violence, the repercussions of violence, and how to process violence in general. These are all mental health skills, if you think about it. It's the reason there's derision for chickenhawks, politicians who advocate war without having the military experience to put it into proper context.
I'm not going to say violent games are good for kids. It probably depends on the kid. If we're going to encourage our children to pursue adult activities, we need to make sure they have the required maturity. From what I've seen, parents generally know if that's their kid. I would argue, however, that the games we play are constructive, tend to encourage intellectual activity and creativity, and are often performed by the smart kids. Knuckleheads have neither the patience to paint an army or the ability to comprehend the complexity of Dungeons & Dragons.