The same is currently happening with Forza games (at least Horizon ones, not sure about original Motorsport series). You can only buy the latest game, others have been delisted. You can still get physical copies, but the DLCs have been delisted as well, so you can't get the full version, at least not officially. And more than that, the online servers have been shut down as well.

It baffles me that this is still an issue, publishers are not concerned with implementing some sort of "kill switch" for expired content to keep getting money for the games. GTA also suffered from this.