I think the one that bugs me is when an outfit on the Mog Station has multiple components, but you really only care about a few. With quest rewards, you can just go to a calamity salvager and get them again. But cash shop items, it feels hard to throw out the ones you don't care about. At the very least, since we paid actual money for them, they can justify the architectural burden of us being able to store them in our armoire.