I agree, all playfields will be better protected if waxed. Although, I've got a slightly different way of thinking about the way wax protects a playfield than most others have described it.
I think we all agree that a pinball with fine scratches all over it is the equivalent of a fine sandpaper covered ball. The "protection" provided by the wax isn't that it is harder or more durable that a clear coat though. It's that the wax provides a layer of lubrication.
A dry piece of sandpaper sliding across a clearcoated playfield is going to continually remove finish over time. The rate of removal will depend on how coarse the sandpaper is (in this case, how scratched the balls are). If we apply some wax to our playfield our fine sandpaper then slides smoothly across it, reducing the scratching. Part of the protection also comes from the fact that the sandpaper is picking up the wax, filling in its abrasive surface, and itself becoming lubricated. When the sandpaper is covered with enough wax it won't scratch anything. Over time the wax will eventually wear off and the abrasiveness returns (time to rewax)
The distinction is important because, in my view, it doesn't matter if you get wax on to every part of your playfield you want to protect. You just need to get enough wax down to continually keep the surface of the balls lubricated. It also makes the case for periodic waxing of the balls themselves. By this logic, Pledge does provide protection, it just doesn't last. If you want to Pledge every few days your pins will be protected (and play like lightning). The reason carnauba is nice for pinball is because it is convenient and stays in place as a lubricant much longer.
The other part of the playfield wear equation is minimizing the amount of scratches on the balls. Change them often and keep your playfield waxed and your playfield is going to last.