When the drag link is on the left side of the car (dirt) the left front wheel will rub the drag link when you turn to the left...doesn't really take very much wheel input to make it rub. once that happens, the LF tire stops rolling, effectively applying a brake to it. Also, when it hits, the wheels really can't be turned any farther left. On dirt you don't have to turn left very hard so having the drag link on the left lets you REALLY crank the front tires to the right, dang near fold them over if you need to, to negotiate being sideways.

Conversly, on pavement, if you have to turn right very far you are in trouble anyway so having the drag link on the right allows you to turn the wheels very far to the left without anything binding up.

I have Zero asphalt experience beyond karts but i have been told that the right hand steering on pavement gives the driver a better feel of the right front and makes the bump steer characteristics more positive for pavement handling.