Exactly this, and in fact as seen with CSGO skins / keys, steam had tradable skins which meet all the definitions of an "NFT" without blockchain. They've been

Exactly this, and in fact as seen with CSGO skins / keys, steam had tradable skins which meet all the definitions of an "NFT" without blockchain. They've been winding it back best they can ever since because having a tradable USD proxy (keys) led to money laundering and under-age gambling websites where people used "keys" as a proxy for dollars so eventually they had to make the keys non-tradable. The cat was out the bag and too late to make the skins themselves non-tradable, but it's worth noting that other companies haven't tended to follow suit in having their skins fully marketplace enabled. There just isn't the incentive for one, why would a company want people to be able to resell skins when they can just sell a fresh new copy at full price.