The automotive industry is learning a lot from other industries, but with the introduction of the electric vehicle, they are truly catching up on some fields that were avoided in the past. One such a field is the application of carbon fibers, where makers of race cars, airplanes and windmills have been in the lead for so many years now. The rise of the electric vehicle has refocussed the attention of the automotive on carbon fiber again, with the likes of BMW and Tesla opening the gates and eyes for many others in the quest to create lighter cars. Lighter cars equal a higher efficiency and for electric vehicles, a higher range. The early users
The first large scale users for carbon fiber were the aviation, windmills, sports (sailing, biking and race cars). For the aviation it allowed for large and lightweight construction of wings and the hull. Lighter airplanes can go farther on less fuel and have more airports to land (heavier airplanes are not always allowed to land on every airport). Wings made out of carbon fiber also have a higher degree of flexibility than a metal wing, which might break under certain loads. This is also the reason the windmill industry is using it for their large blades; to prevent them from breaking under the load of the the wind and reduce the weight of the structure. In any sport having a lighter vehicle (a bicycle, boat or car) means you can more easily achieve higher speeds. Cyclists in the Tour de France or Formula 1 cars utilize the strength and the lightweight properties to achieve the best results in sport.
Carbon fiber has been avoided in the past by the automotive, as it is quite expensive to manufacture and the need for lightweight cars was not really present. The internal combustion engine allowed for plenty of energy to be carried along, which in turn led to allowing huge, inefficiencies to exist. Read: large, bulky cars, guzzling cheap fuel. With the electric vehicle, weight is a more important factor, as a lighter car can travel longer distances. Many car manufacturers have gone through some degree of putting their vehicles on a diet, using aluminum parts, smaller cars and some other tricks.
Tesla had adopted the bodyworks from the Lotus Elise, which was a sports car made for speed and less a focus on cost. The expensive carbon fiber was less of a problem here. For Tesla it was a cheap way to get a light vehicle without having to develop it from scratch. Also BMW saw the potential for carbon fiber early on, they have invested a lot in manufacturing plants and research with the aim to reduce the manufacturing cost for carbon fiber. They have come a long way in doing so, creating the i3 and i8 for prices that are comparable to the vehicles of their competitors, but with lots of carbon fiber in it. In fact, for the i3, the passenger compartment, or the monocoque is made entirely from it.
The BMW i3 and the i8, made with a lot of carbon fiber - Link
More is better. And cheaper.
In the economies of scale, the price of products can often become lower when more of a certain product are being made. The same holds for carbon fiber. With the demand for carbon fiber increasing and the efforts to reduce the cost of manufacturing by for example BMW, the price of carbon fiber has come down a lot. I expect to see a lot more carbon fiber on the road as it becomes cheaper and electric vehicles know how to get more range from it.