The left seat's cable connects to the right pedal of the left seat. The right seat's cable connects to the left pedal of the right seat. The cross over in the empennage allows the cable to pull on the correct side of the rudder horn.
Example: When the left seat pushes the right pedal it needs to pull the ride side of the rudder horn in. If that cable didn't cross over, it would pull the left side of the rudder horn.