In 2005 interview, Lucas said part of his goal with the creation of the second trilogy was to change audiences’ perspective of Darth Vader in the first trilogy. “In IV, people didn’t know whether Vader was a robot or a monster, or if there was anybody in there. This way, when you see him walk into the spaceship in Episode IV, you’re going to say, ‘Oh my God, that’s Anakin.The poor guy is still stuck in that suit.’ So the tension and drama is completely reversed.

From Star Wars Complete Visual Dictionary