I make both wood signs and framed wood signs.
I thought I would explain the difference between the two types today.
Generally speaking, the framed wood signs are made from 3/4" good one side plywood. Most everyone knows how awful the sides of plywood are which is why I frame them. It adds a little bit to the sign...makes it a little bigger, covers the rough, raw edges and dresses the whole sign up.
My regular wood signs are made from pine. The pine wood I use has nice edges which doesn't make it necessary to frame them. I often route the pine edges just to give the edge of the sign a nice rounded edge.