The quick answer would be; because they are enjoyable, but that doesn’t really answer anything. The real question is, what makes video games so enjoyable that more and more people are picking Video Games as their primary pass time. Scott propose that their Glued to Games, Video Game’s appeal lies in their ability to satisfy three core human desires; Autonomy, Competence, and to Relatedness.
This relates closely to the idea of Agency; the ability to take meaningful actions. Life is chaotic and we can often feel like just a pawn in the grand universe. Gaming provide us with an opportunity to feel in control and do the things we want to do, to accomplish something in order to prove that our existence is meaningful. This is desire for accomplishment is what drove Socrates to endured poverty and humiliation in search for the Truth, and what made Edison preserved through all the sleepless nights to invent the lightbulb. Gaming provides us with an opportunity for accomplishments, however trivial. Most obviously, this come in the form of Achievements for something the player did in game. But it could also be as simple as finishing a game. There is a particular sense of accomplishment when you get to tell people you spent 300 hours to catch every Pokemon, or spent 700 hours exploring every inch of Skyrim, or even just finishing the Mass Effects Trilogy in one week.
Simply being able to do what we wish is great. In games, this could mean literally being a God to your own people in Black and White, or feeling like your choices is making a difference in The Walking Dead, or even knowing you are better than someone else in Tetris, of Starcraft. However for some, it’s not just about doing, it’s also about doing it well, and being better than others. Indeed competency in any area of life, even in a particular game such as Doodle Jump or Bejewelled can give the players the sense that they are in control. The idea is that being able to put work through something and see yourself improve provides confidence, which in turn results in happiness, even when the skill you’ve learnt affects nothing else in your life.
Relatedness (with both meat and digital characters)
Humans are social creatures, and we desire the company of others. As such, if a particular form of entertainment can provide us with a means to connect with others, then it will appeal to us. In fact, One of the main reasons Nintendo Wii outsold both the Xbox 360 and the PS3 was precisely because of its focus on party games. The recent rise in MOBA games such as League of Legends and Dota 2 can also be attributed to our need to communicate and cooperate with others. Further more, our desire to connect is satisfied not only via Multiplayer games. Consider RPG such as Dragon Age: Origin, where players experience camaraderie or even romance with in game characters. Even though we know cognitively that these characters aren’t “real” per se, we can get attached emotionally nonetheless.
Most games do not try to satisfy all of these desires, however all games strives to satisfy at least one of these needs. And depending on the gamer’s particular need, they would be drawn to different types of games.