For comparison purposes only (I'm not a tree hugger, I'm an engineer): Gasoline engines in cars are extremely inefficient - 20% or less. Electric engines are very efficient 90%+. So if we could replace millions of inefficient engines with efficient engines we would overall get more bang for your buck (energy useage) with an electric motor than a gas motor.
With respect to power plants: they are more efficient in burning hydrocarbon fuels 35 to 40% than an individual car. So comparitively you have maybe hundreds of higher efficiency power plants as opposed to millions of lower efficiency car engines. Not only that, power plants can also use water, wind, nuclear and solar sources to produce electricity.
Nothing wrong with making engineering improvements over what we have. If everyone thought otherwise we'd still be driving wagons with horses pulling them or model T's or ...Hey if you could buy an electric car that gave you all the price and performance of the car you own today it would be nice - but the technology isn't there and may never be there.