Rockstar Games have been operating via Steam for a long while now, with the mandatory Rockstar Social Club login for online features. Now it all changed, possibly in anticipation of Red Dead Redemption 2 on PC.
Rockstar Games released their own game launcher on 17 September 2019 with no announcement. Players who used Rockstar Social Club for any of their games were greeted by a surprise download that could have tricked them into believing it's a new update for GTA V or something along those lines.
As it turned out, it's another launcher now that all games made by Rockstar will require, on top of any other launchers currently running. Naturally, this is another inconvenience pushed on players as the loading time is longer now since two online checks are necessary along with booting another application.
Some players noticed they can no longer play GTA V offline while on Steam, following the Rockstar Launcher release but the company has revealed this is not intentional. The Rockstar Games has this question listed and the official statement is that the inability to go offline is not intended, developers are aware of the issue and are working to fix it. Players are generally displeased with the addition of yet another launcher but additional DRM is clearly not the focus here.
On the bright side of things, Rockstar didn't release the launcher empty-handed. Those who download it will get a free copy of GTA: San Andreas in case they didn't have it before. In case you didn't play it before and don't mind the dated graphics, GTA: SA is a must-play for anyone who likes open-world games.
Considering that Rockstar are all but officially gearing up for Red Dead Redemption 2 release, it's highly possible they rushed out the launcher in order to be able to bypass Steam when it comes around. GTA V is one of the biggest earners ever in the gaming industry and it's not hard to figure out why Take-Two Interactive didn't like sharing 30 per cent of those spoils.