When Blizzard created Diablo 3, they decided to take control of this market by adding the Auction House, an online exchange if you will. They argued that with it players could more easily trade their items and be protected from getting their money stolen. (And of course, Blizzard could get a cut.) However, for it to work, Blizzard had to mandate that everyone play the game online, even if they just wanted to enjoy the story in single player like the previous games. Otherwise people could have abused the system by hacking their copy and/or pirating the game.
Like Obamacare’s exchange, Diablo 3’s launch was a disaster, with most players spending days after its release staring at error screens instead of playing. People who did get in were plagued by bugs that lost their items, progress, and in some cases, entire characters. The dreaded Error 37 even became a meme for a time.
Eventually the tech problems were sorted out, but then a new issue began to emerge: the existence of the Auction House totally undermined the gameplay. The Auction House had actually made it easier to just buy loot rather than work for it in the game, and further, the transitions between difficulty levels punished players that didn’t use it because the game was designed assuming they would. Since the attraction of continuing to play up through harder difficulties is to get epic loot, and the Auction House has the epic loot, why bother to play?