Because they help with moderation? And I imagine if they do something stupid enough to warrant a block it may very well cost them their position too. If you have a problem with any of the staff members there is a link to the form you can fill out at the bottom of the page.
Sorry, but that is kind of a, to be blunt
stupid reason
It's nothing serious, it just goes down like this
Let's paint a hypothetical situation
topic gets brought up
I disagree with the view of the other person, but I openly state I have no desire to argue about it, so I state a desire to not argue about it and just drop it
the Volunteer in the chat room, does not drop it, and seems entirely unwilling to do so, but I still would like to talk to other people in the chatroom, so to avoid his/her attempts to bring me into the discussion/argument again, I seek to mute his chat temporarily
I find I cannot
I'm sorry, but unless you're a moderator, as far as I'm concerned, you have no right to force me or ANYONE ELSE to listen to you jabber at them if you don't want to talk to them, for any reason unless it is official business.