Why are door handles placed towards the corner of the door?

The door-handle is usually on the opposite side of the door from the hinges to give the best leverage on the door, ie you need less force to pull the door open. You are producing a torque on the door. (Torque is a rotational force). Essentially, as you apply a force to rotate something, less is needed to cause rotation if you apply that force further away from the center of the rotation (in this case, the hinges). Try to push open a door by pushing on the door very close to the hinges, and you will find that it is quite difficult.