The reason we transform energy from one form to another is because different end uses require different forms of energy. 

For example, sometimes we want electrical energy to power light bulbs that change electricity into electromagnetic radiation, some of which is visible as light. 

At other times we want the kinetic energy of a rotating shaft to provide mechanical energy to propel an automobile, so we transform chemical energy from fuel into thermal energy in a car engine, and then into the kinetic energy of the rotating crankshaft that provides power to turn the wheels.