The final drive has to strike a balance between torque for negotiating inclines and top speed, as the electric motor cannot rev to infinity, neither can the power systems handle infinite power though them.
An electric car with a two-ratio gearbox would be ideal for both taking off from a standstill and top speed.
This market in the EU is primarily serviced by diesel 4x4s. I can see a future where the diesel engine is banned and only at that point will something fall out of the woodwork to cope with that towing capacity.
Many of the parts on electric cars overheat when pushed pretty quickly, and while adding cooling similar to a traditional ICE seems to be the answer, it adds even more weight and complexity to a platform which is already fighting to save every oz.
Even the Tesla Model S can't do more than a single lap around many tracks without overheating.
The rear wheel drive versions have a single ratio which has to strike a balance between speed and torque.
This is also the reason that the AWD versions are faster than the RWD even though they are heavier due to the additional motors.
Source: http://www.autoblog.com/2008/01/23/breaking-tesla-has-a-solu... and Ashley Vance's biography of Elon Musk.