First, this is arcade game, not sim. The main target of this game is casual gamer who doesn't know car setup basics.
Second(this is dominant reason), in this game, we can only change setup parameters in some predefined small range, not absolute values. In each track, basic setup values are defined by CM, then we can adjust those. So, 11 at monza doesn't equal to 11 at monaco.The worst part is we never know absolute setup value. That makes you confusion.