Maybe they aren't so great at changing the coding with a battle system? maybe if said people started working on it they would just slow up the process or make it worst? I can come up with a lot more but you get the point. Since you don't know these people you do not know their area of expertise or what they lack. I'm sure Yoshi-P has the best possible people in their needed positions.
A MMO needs holidays to bring the world to life. There are also enough people that love the atmosphere and content that comes with it.