Microsoft has made several attempts over the year to get into your car with units like the Sync entertainment system used in many Fords. While its efforts have steadily improved, it hasn't quite taken over the industry.
Part of the reason is that cars are developed years in advance, and they aren't very easy to upgrade. So the technology is going to be old as soon as you get it, and goes even more out of date very quickly. Dedicated car units just can't keep up with standard computers, and especially not with smartphones and tablets.
That's why Apple and Google took a different approach for their CarPlay and Android Auto systems. Instead of having a built-in computer, your car links up with your smartphone and uses it to power the system. The only thing the car has to do is display the information in a road-friendly way.
Microsoft revealed last year that it's working on a similar system. Now it's taking that concept to the next level by integrating Cortana.