They could have easily crammed the Steam Deck full of stuff to make it hard to use for piracy - locking down everything, making it usable only to play games you legitimately own, force you to go through who knows what hoops in order to play games on it. That’s what Nintendo or Apple or most other companies do.
But they didn’t, because they realized they didn’t have to. It’s 100% possible to put pirated games on the Steam Deck - in fact, it’s as easy as it could reasonably be. You copy it over, you wire it up to Steam, if it’s a non-Linux game you set it up with Proton or whatever else you want to use to run it, bam. You can now run it in Steam just as easily as a normal Steam game (usually.) If you want something similar to cloud saves you can even set up SyncThing for that.
But all of that is a lot of work, and after all that you still don’t have automatic updates, and some games won’t run this way for one reason or another even though they’ll run if you own them (usually, I assume, because of Steam Deck specific tweaks or install stuff that are only used when you’re running them on the Deck via the normal method.) Some of this you can work around but it’s even more hoops.
Whereas if you own a game it’s just push a button and play. They made legitimately owning a game more convenient than piracy, and they did it without relying on DRM or anything that restricts or annoys legitimate users at all - even if a game has a DRM-free GOG version, owning it on Steam will still make it easier to play on the Steam Deck.
Fundamentally I don’t really know how it’d be viable to truly “own” a specific copy of something, when it’s always possible to make infinitely many copies of it. Any such “ownership” is at best essentially just conceptual, aside from perhaps the legal right to annoy other people about the copies they are in possession of.
So instead my personal take is that I’d rather everything just be offered DRM-free. I don’t necessarily need transferable ownership as much as I just need proper and guaranteed access under my own control after I purchase the product.
NFTs cannot have copies made (apart from by the publisher) and are ideally suited to this problem
But anything that exists as digital data can be copied. The same applies to NFTs. Make an NFT image or game or whatever, and it can be copied by whoever has access to it. The only way to prevent such copying is to not release it at all.
The only stipulation is that copies made without authorization of whoever holds the rights to it would not be “official” instances of the thing, and there are potential copyright restrictions on the use of such copies…but that’s using NFTs to justify copyright law, and aside from “lol copyright”, legal of ownership of an NFT is even more of a mess than traditional legal ownership of an IP.