For those we don't get it.
It is like paying for new dungeons (costumes) and then pay monthly to be able to play in them (wardrobe), this is where the friction comes from.
Like mentioned it is counter productive, NCsoft wants to sell outfits and then on the other hand limit how many you can buy because of the storage space.
Also many people have a "wallet" they are willing to spend monthly on a game, lets assume that is around the $15 which is really reasonable since that either buys you a sub or in game goodies in f2p games.
However in BNS if you want to buy those fancy outfits... you also need to have the wardrobe to store them and that will put it over budget.
Many will decide not to buy anything then most likely and spend their money else where.