I guess there are a few concerns here. What if the game developer goes out of business, or dies, or accidentally drops their db? What happens if they decide they don't like one of their collectors and want to wipe their balance clean? (Of course, you could do this with NFTs as well, but you'd have to write it into the contract ahead of time).

On top of that, the developer would need to build and operate their own infrastructure for trading with the tokens. If they were NFTs, then they just slot into existing applications without any extra work.