I believe you are speaking of the overflow tube. Someone correct me if I'm wrong, but what I think the reason for it is to allow a place for the suds to go if too much detergent was added. It also could be in the case of an overflow, the water would not come out he top because the macine is designed with the outer tub seals on the cabinet top. Thus in the case of an overflow the water would come out the lid opening instead of the overflow tube. Also, since they are spin drain machines, If it spun and didn't empty fast enough or not at all, the water would come out the lid without the overflow tube.