Most sites in mobile view offer option in the footer to switch to full site view or desktop view because in mobile view some features or functions are hidden and some users might want to see the full site view to access those features. Here's an example from m.zappos.com:
However, zappos.com also has a "Mobile Version" option on the desktop site so users can switch to mobile view.
From the UX stand point, why? What are the benefits of providing "Mobile Version" option in desktop view?