Since the invention for apps for phones, games have been the most popular category when it comes to what apps are downloaded. Everyone likes to kill a bit of time, wherever they are. And now that so many people have smartphones, many people play games on them instead of buying games consoles. It's produces a whole new industry which actually makes a hell of a lot of money. For example Angry Birds makes $1 million a month from Android alone. That doesn't include any the iPhone or any other platforms.