As you write that it makes sense, but why wouldn't the company make a great, meaningful, ONESHOT game, and then sell a sequel that is also great? Then they sell even more copies because there are no used versions of a brand new game?
I buy every single version of the sims because they are hella fun. Could I still be playing (and enjoying) sims 2 ? Heck yeah, but EA is smart and made a sims 3 for me to buy, which I (and millions of others) promptly bought. I argue that sims 3 is still a great game with many improvements over sims 2 so it cannot fit into your scenario of a shitty game.
Keeping the context of only good games, it only benefits a developer to release new versions rapidly as opposed to making fewer, but replay able, games- as long as the games are good.
Edit: I'd rather George rr Martin release new books than write one book that is fun to reread. Sure, I have reread books, but that is less ideal than having a new book.
(Trimmed the quote ladder for brevity's sake!)
I wouldn't use the Sims series as an example, as I (personally) think Sims 2 was a big improvement over The Sims, and Sims 3 was a...well, not as much of an improvement, but enough that I bought it as well. It had some innovation. It wasn't effectively the same game rebranded, which is the real target of my ire here.
The fake example I gave, of the typical (in my eyes) sporting franchise game, was picked because it's one that I particularly think exemplifies the "just put a new coat of paint on it, label it '2013' rather than '2012', and sell it again at the top price" mentality. Realistically, the differences (in my personal view, I'm aware) between year-on-year games like this, in terms of gameplay, are minimal at best, and I think it's incredibly disappointing how lazy and uninventive it makes companies that can churn these games out, at top dollar, without having to do anything other than change the title.
If people can re-sell Sports Franchise 2012, then that lets market forces determine a fair price for the product. If Sports Franchise 2013 is released, it means that those people who want to play the game but really don't care about the 'paintwork' can buy Sports Franchise 2012 at a lower price, rather than being forced to pay an artificially inflated (monopolised, in effect) price for what is effectively the same product.
Personally, when Modern Warfare 3 came out, I didn't buy it. I bought Modern Warfare 2, pre-owned, and played that. Because frankly, there wasn't nearly enough change between the two to make it worth an extra £30 from me.
This enables that same ability, but for digital downloads as well as physical disks. Which is why I view it as a positive thing. You want me to pay £50 for your second game rather than £20 for your first? Then your second game better be £30 more innovative than your first - or at least £30 more current, or at the very least £30 more entertaining, which is the bottom line here.
To put this another way: imagine you really want to play Solitaire. You can buy a second-hand copy of Solitaire for £3 from someone selling it second hand. Or you can buy Solitaire Deluxe Super Awesome Edition, which simply changes the background colour from green to gold, for £50. Which one will you go for?
Now, imagine Solitaire Deluxe Super Awesome Edition introduces a massive single-player campaign, enables multiplayer mode, updates the graphics and sound to 2012 standards, provides a huge in-depth plotline that tugs at the heartstrings, and incorporates procedurally generated worlds in which to play, providing a level of replayability unprecedented in gaming until this date, which will give you hundreds of hours of new, exciting entertainment.
Now which one are you going to buy?
...jeez, that was an awful and rambling example. It's late, I'm tired, that's my excuse.
Edit: after all that, to answer your point "why wouldn't company make a great one-shot game followed by a better sequel": because, with resales forbidden, they don't NEED to. They can churn out the same crap and still sell it for top price because there is no competing market. If there is a competing market then companies that DO make better sequels will fare better than those that DON'T. I agree that, in an ideal world, they'd do this anyway...but they don't.