Stupid question, I’m sure, and there’s probably some really simple reason. Is it because it blocks visibility? So why doesn’t it block visibility on the back windows. The regular defroster never works so well as those wires do.
Simple. You have hot air blowing in the front from the heater. But it’s hard to pump hot air all the way to the rear window, so they have to make do with the more expensive (and arguably, slower) option of embedded defroster wires.
Visibility. You are much closer to the windshield, and are looking through it most of the time. The rear window is farther away, and you usually only glance through it briefly.
I’d find it really annoying to look at those wires ALL the time.
Actually, I should have known the bottom line was expense. Visibility is good and all but if it was cheaper to do it the other way I’m sure they would…capitalistic society after all.
Not that there’s anything wrong with that!
Some Ford products DO have defroster wires in the front windshild (and some Olds, too). They are fine enough that they don’t block visibility, but they block signals for transponders (toll tags) and radar detectors.
Actually, I rented a Ford Mondeo in the UK in 2001 and it had extremely fine zigzag wires embedded in the full width of the windscreen.
Since it was January, I got to test the usage on a daily basis.
It worked perfectly – my windshield was clear in a minute after I started the car.
I think it must come down to rigid DOT requirements in the US about windscreen glass.
Insta-Clear glass was/is sold in the USA.
There are many cars in the USA with this feature.
I have a 2000 Subaru Forester and it has defroster wires at the bottom of the front window where the windshield wipers sit.
The wires in windshields are embedded between the layers of glass. On the rear glass, it’s done with conductive paint on the inside surface of the glass.
I own a 1995 GMC truck, and I nearly had an electified windshield. It was an option, and I ordered it. When the truck arrived without the wires, it was explained that optical distortions had caused them to discontinue the option. Optical standards are higher up front than in the rear.
From what I’ve read here, that problem has been worked out.
In the car I used, it worked much better than the heater-powered defogger.
Rather than having to wait for several minutes for the engine to heat up sufficiently to begin to melt the ice, the defroster wires loosened the ice within a minute or so.
And you don’t really see the wires since they are hair-thin.
Ever since that week with the British car, I have wanted one on my American car. Oh, and the car wasn’t a high-end model, so it isn’t necessarily expense.
My friend’s 2003 Land Rover Freelander has 'em. You don’t notice them after a while and they work great.
Do they defog as well as defrost? I loathe window fog with the heat of a thousand suns.
As previously mentioned, some models of Ford cars in the UK have the tiny zig-zag wires in the windscreen to demist the screen.
Ford own Land Rover, Jaguar, etc and their cars sometimes have it too.
I think that Ford might have some sort of patent on the system as I have never seen it on other cars.
I’ve had them on all three Land Rovers (2 Discos and a Range) and I don’t even notice them.
Handy as hell in the snow! I have the heated seats too- so even if it’s cold outside, my butt is toasty! 
LR was doing it before Ford aquired them, so BMW must do it too…
As an aside most military aircraft have this feature, in the form of an embedded gold mesh. Works great, but would make a pricey windshield for lower priced cars. Great idea though!
Not only military aircraft, but pretty much any jet or turboprop aircraft. I never get tired of sitting there waiting to push back when snow is falling. With the windshield heat on, the flakes just about vaporize when they hit. (Or would that be sublimate?)
I really want it on my car. It works way better than the defogger in the front. Lines all over the window, or just hot air blowing up from one direction? When cold enough it doesn’t even make a difference with the hot air.
I’m fairly sure our Ford Galaxy had this feature. We’ve replaced it with a Renault Espace however, on which you push a little button and the external temperature goes up five degrees.
I keed. But not by much