For one reason:
We have recourse to those that govern us.
We know who they are, we know how large their wallets are, and can track their actions on the site.
For example, we can monitor the posts they upvote and those that they flag.
We can even determine whether certain members are likely to be in collusion (I don't mean this necessarily in a negative sense), from aligned voting patterns for example.
Our fiat rulers would perhaps shudder at the thought of such transparency - lest transparent, immutable records of their underhand dealings be subject to public review.
Which stands to reason.
Why expose your actions to such large attention? It is only in their interests to seek obscurity...
But transparency benefits us, the people.
No influential can manipulate the content that ends up on the front page without us knowing.
No witness can be demoted without us knowing.
No SP can be dumped without us knowing.
And we know who are rulers are, we know who the influentials are (witness lists, and richlists)
Finally, a system where the masses have recourse to their rulers.