Bicycle Mechanics - Crossing derailleur cables

I've noticed that some road bikes have derailleur cables crossing along the down tube. I assume this is caused by routing the cables from the shifters to the opposite side of the headset. The only advantage I can see is that it might allow a wider cable arc, but I've never had a problem with un-crossed. Is there another benefit to this technique?

I've noticed that some road bikes have derailleur cables crossing along the down tube. I assume this is caused by routing the cables from the shifters to the opposite side of the headset. The only advantage I can see is that it might allow a wider cable arc, but I've never had a problem with un-crossed. Is there another benefit to this technique?

It cuts down on the cables slapping the downtube, and looks cooler :beer:

You got it right!
Friction in curves is the major cause of poor shifting problems. Anything that prevents it helps. So if your bike is fairly low, then the cable housings have to do a tight curve to reach the cable stopper on the "proper" side, or a much larger curve to reach the one on the other side. As a bonus, it keeps the housing away from the headtube.
With higher frames, however, there is much less advantage in using that technique.

Another potential advantage is looks. If you run shifting cables parallel to the brake cables, then it looks slightly better to run the shifting cables in a similar curve to that of the brake cables. So if your brake cables run to the other side of the head tube, then it's nice to run the shifter cables the same way.