Question: Why can't steam and other such digital distributors make it so you can sell it back.. but only to them? They aren't prohibiting the reselling, because you CAN resell the game. That way they could sell you the game, then buy it back much cheaper. Just because you can't sell it to your buddies doesn't mean you can't resell the game at all, so you aren't being kept from reselling, you can just only resell to the company you bought it from.
That wouldn't appear to satisfy this ruling.
This was specifically about the doctrine of first sale.
If I sell you an object, making you the new owner, I can't restrict who you sell that object to in the future. Even if I hold copyright over the object, stopping you making more of it, I can't stop you selling
that copy. One I make that first sale I no longer have legal control over the
copy and can't add extra restrictions on your use of it. [I'm sure there are exceptions to this but can't be bothered to dig just now.]
This ruling defined a set of digital goods (specifically those where the license grants the buyer the rights usually associated with ownership) where the first sale doctrine applies.
Putting restrictions on who you could sell objects back to would be a violation of the first sale doctrine as I understand it. It would be a like a bookstore saying you could sell back any books you bought there, but couldn't sell them to another bookstore or a friend, lend them out or give them as a gift.