Typically people don't build features around individual NFTs but NFT collections. If 20k Lara Croft NFTs were minted in a special Tomb Raider NFT collection, then the access to the new skin would be available to any of the owners of the 20k Lara Croft NFTs in the collection. I think the misunderstanding here is that an individual NFT gives unique access to an in-game asset, sometimes NFT collections give unique ownership to a copy of the same game asset.

That doesn’t really change the question, though: the Tomb Raider developers don’t need an NFT to do that, and any other company isn’t going to spend much of their money giving something for free to a handful of someone else’s customers. Why spend time on that instead of, say, charging $10 for the homage DLC which gives them actual revenue and from a much larger number of people?

For example, how many of those NFTs would have been lost or stolen — and do you want to tell potential buyers “sorry, nothing we can do about it - blockchains mean no margin for error!”

Fair enough, creating an asset which 20k people with access to a collection theoretically might use is more attractive than creating a unique asset for a unique token. It does seem strange that the supposed "killer app" for NFTs in exchangeable game stuff wouldn't have any use for their core feature (uniqueness on the blockchain) though.

If a developer wanted to market games by offering inducements to players of other games in the form of unique content it seem like a lot of other solutions would be more attractive than the blockchain. Partnership with other developers or platforms like Steam gives you an actual marketing channel to hype the special add on for Tomb Raider players, and to a lot more than 20k people. The only case where I can see them preferring to attract small numbers of players of a third party game who paid that developer for NFTs rather than every player of that game is if their game is pure pay-to-win bullshit and there's no point in targeting the sort of player who doesn't buy NFTs...