Good question - Couple reasons. 1) It is easier. Especially at the landing. Just drop the hitch and pull forward a little with some cable slack and unhook the chokers. Then winch the cable back in and you are ready to go again and the chokers are still in the sliders. 2) If you have a winch with a lower pulley and you put the cable in the lower pulley when you are ready to skid out it keeps the pulling point weight of the logs low just the same as if they were in the slotted bar. 3) In the woods if you have to drop the hitch, drive over a rough or very steep spot, and then winch the hitch back in you don't have to mess with taking the chokers out of the slots and put them on the sliders to winch and then put them back in the slots again. Even with my small winch with no lower pulley I leave the hitch on the cable if the going is good and the hitch not to big, Those are the main reasons anyway.
gg