I know there are people who have those no-armour value outfits like the pants and shirts that you get when you make a character. And I also know there are people who have been wishing they could use these over the top of their armour like they can with costumes. I'm one of them.
The idea is to have an npc or even just a window tab in collections when you pay 400 crowns to convert a single item to a costume piece and it gets added to collections.