Well this is only my opinion , but here it is:
There are a couple of factors at play here and the first that i dont think that you can ignore is the fact that all of the players are so separated in the server, being in their own realms. For me at least, this does take a little bit away from the server, while at the same time being good in that it differentiates it from other servers and allows it to run fine with minimal moderation.
The second, and perhaps most important factor is that there is no real reward for the time that you put into the server. There is no reward for skill in building and because so little moderation is needed (because promos are automatic and griefing is for the most part nonexistant) there is really no way to build trust with the server and become a moderator yourself. (and to be honest it doesnt look like many more, if any, are needed).
But with all of that said i still think that realms is the most practical way for wom's server to be set up. With a community this large, a freebuild style server would take an enormous staff to moderate, and invariably, with an enormous staff comes incompetent staff members.
While i too would like to see a freebuild style server from wom again the server that they have now is probably not going to change anytime soon (perhaps rightfully so).
But thats just my take on it, it seems to be the case to me.