GOG might let you do it if you buy a game from them once in a while. Steam constantly subsidises downloads by allowing devs to mint and sell their own steam keys, I don’t think it’s going to be an issue.
And, yes, you could have a database somewhere – but then the proof of ownership might disappear with that database, e.g. when the publisher goes bankrupt. Also the publisher has incentives to make ownership transfers awkward, slow, etc, the blockchain doesn’t.
Another option would be the equivalent of a central bank, some public institution (as in public law) which keeps the database. But do you really want to register your ownership of a license of XXX Hentai Boobmania with the copyright office?
Don’t get me wrong I’m far from a cryptobro. It’s just that trading licenses independently of stores is about the one thing the tech is actually good for.