I've wondered these questions myself. Surface mounted romex is a big no-no here. Even the home inspectors call it out. As I said in my last post, it's a very uniform rule.
Can you all really just staple romex up to the sheetrock in a garage or something?
I know there is a lot of jurisdictions with some messed up opinions of what needs physical protection. But if you go on what NEC alone says why can't you staple NM cable to the surface in dwellings or dwelling accessory buildings if there is no apparent reason for physical abuse? We can have exposed glass lamps on the ceiling and not require any physical protection for those but a little NM cable is a problem? Does that make any sense? I don't think so.
Get outside of dwellings and dwelling accessory buildings and it usually must be behind at least a 15 minute finish - so you aren't running it on the surface but not for physical protection reasons.
334.15(B) starts off with "Cable shall be protected from physical damage
where necessary" That "where necessary" is what is being over interpreted, in some places to the point you don't run exposed NM cable at all.