Hiii I might be able to shed some light on the technical reasons behind this. It has to do with how often data is modified. Based on the hard statistics we've observed, shops are like THE most active part of the website, since there's constant buying and selling going on, and every transaction has to modify the data (adding or deleting items, along with other stuff like updating shop history, shop tills and stats, maybe alerting the shop owner etc). Vaults and wardrobe don't have a comparable amount of activity; people generally put things into the wardrobe and access the data (by viewing it) but don't remove things too often, same goes for the vault.