I think the reason the two boards exist is that they have different restrictions
Yes but the differences isn't that big.
If anything, they should first get rid of boards like the press board.
That was suggested long time ago but the spam level declined a lot since most signature campaigns no longer counts posts there. Instead many topics shifted to Bitcoin Discussion.
However, Ivory Tower isn't doing any harm where it is... Its existence isn't particularly offensive, and I suppose there may occasionally be times when someone wants to post something and not have the thread overrun by low level accounts or sig spammers.
I agree there is no harm and at the same time there is no point to have another archival-like.
As I mentioned above, signature campaign members avoid wasting their time in both subs since no signature shown in both subs.
I don't have any problem with Ivory Tower or any other inactive sub, I just prefer to merge them with the main one to avoid having so many subs without a valid reason, just like local section. Theymos et al. do not open a new one unless there is sufficient people and posts.