Do you have any idea how to program or what is involved? It has nothing to do with diversity and everything to do with complexity. The interaction between the events is what makes things complex. The whole principle where you have a persistent world make is complex. Things like balance don't come into single player games. It's not relevant. If you look at GW2 and see how many of the initial complaints were about balance you might start to understand how much time they need to spend on development tweaking and testing that balance. People always push things to the limit in an MMO, try and see what can be done. They try and walk through walls to see if they can get a competitive advantage. When was the last time that someone tried to walk through a wall playing skyrim?