First of all it depends on the games you are playing. If you are playing Golf or Bowling it will automatically keep score after everygame whether it be singe or multiplayer becayuse those games are based off of individual skill.
In multiplayer games were you play against someone that is not the computer, Baseball, Tennis, Boxing, they don't keep score cause it not possible to determine your skill level against another human opponment. They could just be letting you win or vice versa, and that could be used to artificially boost your players status up to Pro and beyond.