Well, they could be considering a different camp customer... Who knows, what if you're gutting a fish at your RV, do you want that stuff going into your grey tank? Of course most people would use some sort of strainer to keep that stuff out, but maybe that was sort of the intent? However, with many outdoor kitchens at the last RV show I went to, I noticed that many of them just seemed to have an open pipe that they routed to. I think another poster may be onto something, about the tanks not being far below the sink. I know I wouldn't want water coming back at me, or to find a watery mess after driving from one destination to another.