They are volunteers, yes: they volunteer to be our servants. They should not act on their own initiative, but merely implement the will of the community.
Strictly speaking, you're right, but interpreting the will of the community sometimes requires a bit of initiative. Interpreting the will of those involved in an issue is easy, but it's not always enough. To interpret the will of the community at large requires an understanding of why the community has the views it does so that you can apply those views to new situations - it's these new situations that generally result in cries of "admin abuse" (ignoring the "how is my company going to get any business now you've deleted our advert?!" complaints, which are far more numerous but far easier to ignore).