Not to argue, but there are applications and there are applications.
Some of which will tolerate a touch of back bevel, and indeed function better with that…
I think of my adzes, where the mere touch of a back bevel allows the "wedge to ease itself up and out, instead of digging in.
The simplistic description of a wedge that steve describes implies that there are equal forces on both sides, but we all know there ain't…maybe a mere 1/10th of a mm on one side, but an inch or two on the other side. The physics of a simple wedge cannot apply without considering the forces directing that force.
OTOH, if yer paring edge banding off of a panel with a 1/32 veneer, yer back better be absolutely flat.
And if you have to pare a 1/4 mm off of a tenon on an expensive antique undergoing repair, you want to be certain that the first chisel you use has the same characteristics of the one you pick up next, and will cut the same. Easiest to do if the back is flat on each and every chisel. OTOH, you might be able to fuss around with variably sharpened chisels trying to find the one that will follow a flat…till you found one that worked.
Besides, when yer sharpening the chisels, how do you figure out how much out of flat the bottom is, so as to take off the wire edge.
I however appreciate and understand where yer coming from steve, some of my carving tools, adzes, and particularly the power carving tools have a deliberate back-bevel (unflattness) to allow them to defect up instead of down….And when I'm rehabbing old tools, sometimes I just do the best I can, and hope for flatness in future rehabs. There is a law of diminishing returns, and sometimes you just have to accept a less than perfect , but perfectly usable result.
Eric in Cowtown.