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.

No, it wouldn't have been possible. Because nobody (read: secondary-market game collectors) is willing to be on the other side of that deal and actually value these transferrable game licenses to the degree that they value physical games. Because, in turn, the hypothetical little by-fiat "federation" of companies willing to honor it could just decide to renege on the deal at any time and stop honoring it. (Which would probably include shutting down the database that remembers who owns what!)

The point of putting a blockchain in the middle is that the immutability of the smart contract underlying the tokenized asset guarantees that you still own the thing even if the person who sold it to you disagrees, and the person running the show backs them up†. Which is not true in the by-fiat system.

To put that in terms of non-digital assets: a country that issues a fiat currency, can declare at any point that some asset token they've issued is "no longer legal tender." Canada did it with pennies a while back. But they can't declare by fiat that a commodity has no value. Commodity values can be manipulated (see: oil prices), but they can't simply "make it go away" by withdrawing their backing from it. A commodity has inherent value, whether or not it's backed.

(How would that work, in this case? You'd need 1. IP ownership [or at least sub-licensable use] rights sold to a legal trust, 2. where that legal trust's beneficiary is a DAO; 3. where that DAO declares in its immutable articles of incorporation that non-fungible tokens issued by smart contract X represent transferrable sub-licenses of its acquired IP license; and where 4. smart contract X is immutable.)

If you've got all four of those properties satisfied, then what you've created is less like a fiat currency, and more like a commodity. The IP owner cannot revoke selling a sub-licenseable IP license to the DAO, any more than you can revoke selling your house to someone. The DAO has no path to change the rule by which it allocates IP rights through the token. And the token itself can't be tampered with to change who owns it. The only place you could affect this system would be at the level of getting the government that issued the original IP license, to declare it void. (But why would they do that? The US government didn't do it for Tolkien's dumb sale of sub-licenseable IP-rights to LOTR in the 1970s, and that was pretty much the case where you'd expect big-Hollywood lobbying to win out over the public good.)

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† Yes, technically, you can also create this guarantee just using the regular legal system, without involving blockchains — you'd issue individual IP licensing "deed" contracts to each primary-market buyer, such that they can prove they own the rights; and players could then resell these "deeds" to each-other with a notarized and registered document of sale, similar to land title transfer, so that you can prove that a given "deed" is legitimately acquired rather than stolen or forged. But that's extremely impractical — the costs of the overhead of the transfer process far outweigh the costs of the goods being transferred! In this sense, a blockchain is just a way to make this process scale for lower-value items, by making the whole "notarized transfer-of-sale ledger" into just some (digitally-signed) bits, such that people can transfer each-other IP rights — and other low-value "deedable" things — from an app on their phone, at the cost of maybe a dollar for "notarization and registration" by the chain's validators.

Even if there was a blockchain, Steam still has to decide to honor it, because they’re the ones who physically decide whether you get to play the game, or not. Nothing prevents them from choosing not to honor transfers that appear on the blockchain after a particular date, thus effectively switching back to a centralized database system.