Mechanical transmissions are still more efficient, at least for cars, than spinning a generator that then powers an electric motor.
Even hybrids usually have a way to get the engine power directly to the wheel. In the Prius's system, it uses a planetary gear with a pair of electric motor/generators which allow it to split power between the mechanical and electrical paths. In the Volt, there are clutches which allow the car to transition between parallel and serial hybrid modes.
Even hybrids usually have a way to get the engine power directly to the wheel. In the Prius's system, it uses a planetary gear with a pair of electric motor/generators which allow it to split power between the mechanical and electrical paths. In the Volt, there are clutches which allow the car to transition between parallel and serial hybrid modes.