Impact severance zones!
Should a dumb Chav step in front of you, if the box section bumper doesnt stop them going over the bumper and into the screen the wires dissipate their full force by.. Quoting mathematical equations Dividing it by two, or rather themin two!
More modern cars have bonded laminated windscreens to stop them flying through.
As A bonus they stop the full force of branches hitting the screen and serve as an aid to pull yourself out the door and onto the bonnet should you so desire.