I view MUSHes as a collaborative story, so keeping elements of the story private runs counter to that general goal. I am transparent by default.
That said, my preference is not everyone's so I can understand those who may wish to not share, or delay sharing logs, hide their backgrounds, etc.
I would challenge the assertion that Ares encourages you to log and share every scene. The server doesn't care if you log (except insofar as you miss out on certain features - like participating via the web scene page or editing poses - if you don't); the server certainly doesn't care if you share. I think the fact that so may people do log and share scenes is more a commentary on the prevailing feeling amongst the players than anything the server is requiring.