That's exactly the whole point of this… The users should have that option to resell their games. Gaming media, social networks and gaming forums should make this topic more relevant.
Yes I understand your point, I'm just saying that most game companies who run digital walled gardens would probably rather close up shop entirely than let people resell digital games. As
simpatico
mentioned above, these publishers and developers have already "lost" billions of dollars to the physical used games markets.
Digital games don't degrade in quality like physical games do. A "used" digital game is identical in every way to a "new" digital game, so there is zero incentive for someone to purchase a "new" game, short of a used one simply not being available (launch day, maybe?). This simply creates the "race to the bottom", because if you can purchase a "used" digital game for $5 less than a "new" copy, then sell it again for $5 less than you bought it for (using nice round numbers here) - it's like you, as the consumer, only paid $10 for your game.
Publishers know exactly how many digital games they sell, and platform holders (Nintendo, Sony, Microsoft) know exactly how many people are playing a particular game at a particular time. It's not hard for them to do the math and know that their number of copies sold would arrive at, or close to, the number of copies played simultaneously, very quickly. Within a week after release, most games would probably stop selling "new" all together. Your total copies sold now becomes roughly equivalent to the number of people simultaneously playing your game. It's pretty easy to see on Steam (with Steam Charts and SteamDB) how many people AAA games retain over time, so this would be devastating to their bottom line.
So let's say your Nintendo, and you now live in this fictional world where you only make profits from your games for about a week after they release. What kind of budget are you going to give to your next AAA game? Would you even bother making one? Would anyone?
The only scenario where selling your digital games makes sense is if the platform holders get a significant portion of your sale. Like... 90-95%. If you sell a game for $50 to another user, you get $5 of that, and they take the rest as the "broker" for that sale. It's the only scenario where they've disincentivized people from wanting to sell their digital games at all, while keeping prices (and their profit margins) high enough to make the whole endeavor sustainable. And let's face it, at this point their just giving you a $5 refund if you opt to remove the game from your account.