Really? Because you just named single player RPGs. Every online game that has expansions pretty much require a player to have said expansions, doubly so for games with an "end game." None of the games you listed have an end game at all. There's a reason so many people compare Destiny to MMO's and its due to the end game, and the way the world and loot changes. Look at WoW, ToR, even non MMO's like Diablo. If there's an end game, you need the expansion. And in 98.88% of these games you must purchase the expansion. The ones where you don't have to are generally pay to win or riddled with microtransactions. Sorry I didn't feel the need to elaborate further, it seemed pretty obvious that I meant multiplayer games.