Why have video games grown increasingly violent over the years?  

Video games have been a means of entertainment for people of all ages for years now. Pong is one of the earliest arcade video games and is a tennis-type game where opponents (or a computer player) try to return the "ball" in a way that the opposing player will miss the next hit. Over time video games have evolved to include better graphics and better game play features. Mario Bros. of the early 1980's still showed pixel images, yet the graphics slowly enhanced -- the main character, Mario, being the protagonist who jumped on the heads of his enemies. Through the 1990's Nintendo came out with the 64-bit platform in 1996, the Nintendo 64--which improved graphics greatly since its 1983 Mario Bros. release. N64 games thrived with 3D images, considering the major improvement since the '80s. Fast forward to 2001 with Rockstar's release of the highly controversial mature-rated Grand Theft Auto III. The game, abbreviated GTA3 displays violent acts of crime in addition to adult references and drugs. In 2009, Call of Duty: Modern Warfare 2 was released worldwide--the highly anticipated first person shooter. Games have gotten so violent over the years. What's up with that?