I'm not entirely sure, but the game disc can still be sold. Isn't it? If it is just a code you enter and then don't need the disc anymore, then you cannot sell it. Its basically a digital code only, like on Steam / PC. But if the game disc acts as a license, then it will download the rest of the game and you still need the disc to play. In that case you can sell the disc and no longer play the game. Similar to how game key cards work on Switch 2.

Another reason why big publishers want to have a physical release is, that they have a presence everywhere where "normal" games are also sold. Maybe your mom buys it for you, or a friend gives a gift.