I think they make sense to keep. Sometimes people click their way into a sub-board, either from the index (with no description) or from another webpage (with varying degrees of context provided.) It makes sense to keep it as an option IMO.
Considering that it's a core SMF feature that's off by default (and is off by default for users), most people have never seen it, nor know what it looks like...
The thing is, I take the view that a description designed for the small confines of the board index (where it might be a 'line' or two there) isn't going to work so well when it has pride of place at the top of the board listing.
I'm not sure to be honest.
That relates to the above point.
Let's take this board, The Pub -> Features. According to the board listing in The Pub, this board's description is "This is the place to discuss upcoming features, existing features and brag about whatever we implemented in Wedge."
It's quite long on the board index, but it's barely a line wide when considered for the inside of the board.
Users should only really have access to options that matter much to them (seriously, even on simple devices, users manage to mess things up.) I say it does good as an admin preference.
That's my take on it too.
As for my personal opinion: I don't know, but I'm sure what you decide on will be a good solution.
That's what I'm hoping to achieve - and I'm thinking about the whole short/long description facility, which implicitly functions as an option for the admin to configure it how they want, and then remove the user option. If the admin wanted it, they'd use it.
Or, I could remove it from display, not bother with the extra, and turn it into a plugin like the 'Board Notice' mod for SMF or similar.