Out of curiosity.

[Arohk]

...I'm not sure what kind of answer you're looking for, but the very obvious one is: Because storing data costs money. So they limit the amount of data everyone of us can store.

I hate to say it, but WoW has a fantastic system when it comes to glamour collection, once you owned an item it is stored in your collection and can be used for glamour, instead of physically owning the thing.
The only difference here is that WoW can't dye items, so im not sure how that would work out.

[Jojoya]

I hate to say it, but WoW has a fantastic system when it comes to glamour collection, once you owned an item it is stored in your collection and can be used for glamour, instead of physically owning the thing.
The only difference her eis that WoW can't dye items, so im not saure how that would work out.

But also as you say, WoW's system doesn't store the actual item. It only records that you've unlocked the appearance of the item. If you want to have the actual item to equip (not really necessary in WoW since you can only level a single class on each character), you need to keep it in your bags/bank or re-farm the item if you sold/discarded it once it was added to your transmog collection.

Here it stores the actual item, allowing it to be removed from the glamour dresser/armoire to be equipped. That's a feature that a lot of players take advantage of because it cuts down on how much gear they need to store in their Armory Chest while leveling multiple alt jobs. SE would probably need to monitor player feedback about how many use the item restore feature.