I am one of those who likes 2.5" bindings and sometimes even cut them at 2 5/8" or 2 3/4". I always sew my bindings on with a 3/8" seam rather than 1/4" and I calculate depending on what type of batting I have used and whether I am going to finish the binding by hand or machine.
Using 2" binding and a 1/4" seam does not allow for the batting thickness, just as others have mentioned. . . so you end up having to pull it tightly in order to cover your stitching line. There will always be stress on your sitching that way and the binding will wear out faster.