I guess the wheel is a response to an unusual cutting task ... a hard substrate (even crispy hard!) ... with a soft squidgy layer sat on it that, for the sake of aesthetics, you'd rather not have ragged about ... cuts clean without any relative horizontal displacement of the aforementioned squidgy stuff.
Having butchered a few pizzas by sawing at them when there was no wheel available it makes sense. 🙂
K
