It depends on the casino. Upgrading popular slots with new graphics, characters, or bonuses keeps existing players and is cheaper. New games can attract new players, but they are more expensive and riskier. Also, upgrades can sometimes be limited by the game’s technical setup or licensing
A constant upgrade on existing games with new features and skins coupled with designs will always keep and attract new players to the casino. This is just the basis for a continuous existence in the gambling space, as it is good for marketing purposes to retain old and new players. Constant upgrading is much better because it keeps players excited about the new features of the games they are seeing compared to the old version, as that keeps them more passionate in constantly playing that particular game they always spend quality time playing, since they have seen something new and catchy to their eyes.