Sex is a natural part of life, and, thus, it is a natural part of art.
In fact the earliest works of art, like the Venus of Willendorf are sexual in nature. So it really should not be a surprise to anyone, from Jack Thompson to Hillary Clinton, that sex would find its way into a video game. While some video games that contain overt sexuality are lewd in nature, like Leisure Suit Larry, not every game with explicit sexual content is like this. The Mass Effect series, The Witcher series, and the Knights of the Old Republic series all consist of narrative based games that feature sex to varying degrees, but in these games, the sexual content is only one part of a much larger game.