Have you noticed the the car mirrors dont reflect any of the car parts. You should be able to see the side of your car from the side mirrors, and part of the back from your Rear View mirror.
I think they show too little of the road behind you in their current form already, adding a "realistic" view on your own car would clutter things up.
The mirrors are one of those things that should not be über-realistic, because in RL you have a much larger FOV and you can see a lot more in the mirrors... Wanting to make those tiny things on a PC monitor show everything you would see in RL is just plain impossible and would make them unuseable IMHO.
Besides being unusable when they were "realistic", it's also not that easy to code a mirror and maintain good performance. So with even more detail and an additional drawing of the cars interiors, the mirrors would suck down performance even more.
I'd also like to see different viewing angles on the mirrors, so not every mirror gives you the same image. If that would work, the sidemirrors would be so much more useful, but you'd have to calculate an extra two viewpoints, which is a big no-no for performance again :/