Why they are in this game and other games is understandable, the fact that they are there in the first place and where they are placed that is the problem. It is a technical shortcut which can be resolved with different map design, or by using invisible walls which you simply cannot walk thru placed in the proper areas. A wall which instantly kills you in a perma-death game without warning is a bit much however, and they are in places that you CAN access anyway (milton from the mountain down to log sort is completely accesable and will not kill you in any way shape or form to explore the area beyond the kill wall in between).
A kill wall at the bottom of a ravine is an example of what you are taking about Fuarian and thats understandable. The ground itself should kill you not the way down, especially if you are climbing down to a completely safe region. In fact the kill walls we are referencing are actually all in areas where you can safely climb down mountains with ropes etc, and do not prevent you from being stuck in any way shape or form.
In fact just today i lost a day 95 interloper because i accidently got stuck by falling to a ledge in milton while exploring and simply looking for a ROPE to use lol, once i fell down i broke my ankle and could not reload, and below that was the basin which is very explorable and i had a path to make it down. However i died to the kill wall on the way, which simply has no place there. So the wall not only preventing me from exploring an area which is open and safe, but actually can be considered a bug which forced me to die.