A crumple zone capable of affecting the deceleration of a 3000+lb car while complying with bumper strength requirements (though today's standards are much relaxed from those decades ago) isn't going to protect a sack of meat from a car. The bulbous front end plastics that take up a lot of space without much underlying structure, flimsty upper radiator core support and thin easily bent hoods are where the pedestrian safety comes from.