What is the purpose of the "tongue" shape of a chair mat?

Question

I am an interior designer and can't quite understand why the shape of a chair mat still has a "tongue." I have yet to see a desk or configuration of systems furniture that needs this shape.

Answer 1

A traditional desk has the section in the middle where one's legs go. The tongue portion of the chair would go in there. My chair mat at work has a tongue that isn't useful. But the one I use at work fits my desk perfectly.

Answer 2

I believe it is for your feet to keep the area under it from becoming worn. It also helps when you push the chair back so the mat does not move with the chair since your feet are on it.