Take two players. Both get on base 40% of the time. Player A has good players batting next in the lineup so he his knocked home 25% of the time. Player B has less capable batters hitting behind him and he only gets home 10% of the time. Player A will score more Runs but he isn’t any better than Player B.
Flip the example around by measuring the batters hitting first and you have the story of the RBI. Even position in the lineup can impact both a player’s Runs and RBIs.
So why do we still measure these values? Habit mostly. Baseball fans like to count everything. They also measure context.