Optimization. The Ram holds the information of what is happening and is going to happen, so if a lot of things are happening (like a big map and lots os models) the ram is going to get consumed. It also depends of the engine, like Sonic's engine, a sonic game could use 2 or 3gb of ram but use 4 or 8 depending of the game, as the engine order all the land to have colision instead of just when sonic is going to touch it, and the same thing happens in competitive games, they need to have all the ground and wall and scenario already in the ram as people will move fast and in all places. But Anthem is really bad, PUBG and fortnite (i got around 60 with 8gb and a 1050 with a Pentium G4560 in fortinite) isn't that older and need just 8gb