Although an official player count wasn't released, its reported that December 2017 was the peak month in engagement for the highly popular video game. This comes as no surprise, seeing as how GTA V sold an astonishing 85 million copies across all formats, making it one of the best selling video games of all time.
If you're wondering why a game released four years ago is still getting so much love, you can thank the games' creators and developers who deliver consistent updates which keeps the user experience fresh and fun. The recent launch of the Doomsday Heists update featured an elaborate heist story, a fully-loaded base from which to order missiles and NPCs and, best of all, an assortment of brand new cars and outfits to choose from. It essentially upgrades the GTA platform to make it feel like a completely new experience.
Based on GTA's rising success, it would only make sense to see Rockstar Games continue to apply their creative minds towards developing new concepts for Online as they've been. After all, money talks.