Its not needed, same with crouch movement. Just a normal crouch is all we need.
It may not be needed, but if things aren't added simply because we don't "need" them, we'll end up with an exact clone of NW. This game has the chance to do so much more, if they go beyond what is "needed".
Another consideration for being able to walk when crouching is to make the most of fortifications. In NW, you have to stand up to move around, whereas if you could walk around while crouched, you'd cut your exposure to enemy fire extensively. Honestly, if crouch walking is present, I would suggest letting all units do it, simply for that alone.