I think you all are thinking too much under the illusion created by SE making it Unique in first place. Maps are IMO not different from any other items on MB. Some can monopolize it? Sure but till what point? And why it would be a problem with maps but not other items already on MB like Zu mount, red script mats, minions etc., ie. high value items that normally gated by time/rng? Why would people buy a stack of maps for an average price 100k each while the items they can get from each maps only worth 20k? And please don't add treasure dungeon here yet, it is still new content. And when it release, the price of maps will spike anyway, until people can evaluate the "worth" of the treasure dungeon. In the end the value will still balance out.

Unable to stack maps surely helps stop people buying all the maps available from MB, but the more realistic reason IMO, is that they stop buying maps from MB when the price starts going higher than what they deemed those maps worth.

The uniqueness is only a delusion, and adds nothing else but inconvenience.