Because it is easier to see when it is about to reach a cut off value. BTW airplanes sometimes used the same layout back in steam gauges era (so you could spot that one of gauges shows values that are out of the order).
Yeah, that trend carried on into the Group A era: Full digital dashes have now rendered the (very cool) rotated gauges out!
Notice that the RPM gauge is rotated in a way where the vertical position corresponds to the maximum torque, or maybe to max rpm (which is i bit higher, depends on the engine's characteristics). That's what really makes sense and earlier as we were building rally cars and racing them this was that we were aiming at. That gauge in the game footage in the Golf II it's now really 180° upside down, i'm not sure it's how it was IRL...
