A few years ago they added a launcher to all rockstar games. Much like the more recent 2k launcher it's really only there to enforce you having an account and to accepting some t&c to play the game. Probably so they can force US people into arbitration, and harvest data.

I recently got RDR2 from Steam. When I started it up, it presented me with a "you must also have a Rockstar account, and accept those T&C in addition to the stuff that Steam already requires. In turn, we will capture information that is entirely irrelevant to you playing the game; and by the way, would you like to subscribe to our newsletter, marketing, promos, and daily joke emails?"