i think it's because.. ig earlier on when the game was more active this would've been more of a problem but getting flooded with spam/people who just want the position to abuse power etc.
staff seem to be chosen by observation of forum/game activity/helpfulness and so far it's gotten fairly consistent results without somebody having to file through application after application.
just my take on it though.
[i have a feeling if they DID implement a application system that.. should drama crop up again.. well.. there are some people who've proven that they think being spammy and whiney actually promotes change. wouldn't really help remedy any situation and instead draw focus away from whatever issue might be going down. again. just my two cents on it.]