Not too long ago we predicted that yesterday's Take-Two Interactive investor call would reveal Grand Theft Auto 5 has shipped 90 million copies, and lo and behold, so it happened. Beyond talking about yet another shattered sales record, the call also gave some insight into how the publisher, Take-Two Interactive seeks to expand on recurrent consumer spending, and there was some discussion regarding Red Dead Redemption 2's recent delay.

GTA 5 has been Take-Two's biggest financial pillar since it launched and a constant stream of revenue both thanks to never-ending sales and microtransactions from the multiplayer mode, GTA Online. Both were hot topics in the call, as no other game could ever even come close to what GTA 5 has achieved recently, selling so many copies so long after initial release.
At this point, it's likely still shipping so many copies due to a kind of double snowball effect. A huge chunk of players still have the game for Xbox 360 and PlayStation 3, however the more players upgrade, the more will follow suit, resulting in more sales. The second layer of the double snowball comes from the fact of there being so many sales in general. Since everyone else is playing GTA 5, the people who don't own it yet figure they might as well jump aboard. Yes, it's that popular.
Online and its constant DLC is also a huge attractor. While over four years of content also made the game feel a tad bloated and somewhat daunting for newcomers, Rockstar recently released paid in-game item packs to make it more accessible to new players, provided they're willing to drop some cash on them. GTA Online reigns supreme as one of the most played multiplayer games across all platforms it has been released on, though it has a comparatively smaller presence on PC.