Lot's of good comments, much appreciated.
I've been using this for about 5 years. Since where I live there is no inspection required, it's not really "all for nothing". My insurance agent walked through recently, made no comment.
I don't understand what kind of physical damage the code generally is referring to. Obviously this would not be good behind large cabinets where one could not see it was pinched. However if I am swinging a piece of angle iron and hit the wire, that's a pretty obvious "repair required".
My wood shop was conventionally wired like a house, Romex through the studs. I've had rats get in the walls and eat the insulation off the wire.

This was my solution.
I've had a couple of EE's look at it, no real complaints from them.
I can run pipe but hate to do it, and adding a circuit can get a little complicated, as everyone who has tried it knows. Unless you terminate every wire in every box, pulling a run means pulling lots of wire, just to add one circuit. Hence the value of cable tray.
Thanks all for the comments, I may just build wooden cable tray for my shop addon, with a cover. That could look slick.