Why are you able to message your friends on Graal? Because the programmers developed a system that would allow users to connect with one another through PM's and other means.

Why are you able to farm and get Gralats, or do that Pyrat Quest for 1,000 gralats daily? Because the programmers developed both of these systems for the game.

They developed the skeleton of how the game runs and the different functions you can do in that game, the graphics artists and such bring that skeleton to life, making it a complete thing.