In beginning people play because they just love it, but they stay in the game for the details. Because you can like characters, maps, lore and especially mechanics that players will spend a lot of time to learn, such as double tap strafe. And then, using it in battle, they will see the result of their action, and this is the result for which they spent time and energy. This is exactly why players stay in the game for several thousand hours. It's not interesting just to play - when you have room to develop, you will spend time on it. It's really important to the game when played for as long as possible.
