I would guess because the in-car navigation is a relatively new thing to car companies, and largely outside the specialties they've developed. Ask a car compan

I would guess because the in-car navigation is a relatively new thing to car companies, and largely outside the specialties they've developed. Ask a car company to design a useful and functional suspension system, an engine, a transmisison, a brake system, and they'll have little trouble doing so. These are all things that rather fundamental to having a functional car, and the car companies have had decades to work out the various difficulties in engineering and building such things. However, a nav system is not (yet) a hard dependancy of a functional car. As such the man hours that car companies (or their contractors) have put into their (non-essential) nav systems likely pales in comparison that Google has put into maps.