Pressed wool felt does not have a weave, which is why it can be cut in any shape without hemming and why so many desk mats are laser-cut rectangles. A laser edge is crisp, slightly darkened, and cheap.
It is also where the mat starts to go.
What actually wears
A mouse crosses the right-hand edge of a desk mat thousands of times a week, at a shallow angle, under load. Pressed felt handles this well across its face and badly at a cut edge, where the fibres have no neighbour on one side. Within a year the edge fuzzes; within two, it thins.
Binding puts a folded strip of woven tape around the edge and stitches through it. The wearing surface becomes the tape, which is woven and can take it.
The trade
Binding costs a slow operation on a machine that cannot be automated as cheaply as a laser, which is most of the price difference between a bound mat and a cut one. It also adds about a millimetre of height at the perimeter, which some people dislike and most never notice.
We bind. If you would rather have the crisp edge and replace the mat, that is a defensible choice — just make it knowing which one you are making.
