Good link! and thanks for enlightening me. If you don't mind, summarizing, the cone is known as a bulb shield or an anti-glare shield for oncoming traffic. A poster in the link stated that the inside of the shield (cone) isn't chromed, so the purpose of the shield isn't so much to redirect the bulb's light back to the parabolic reflector. Also, although H4 bulbs have a blackout tit, it's not enough to shield all the glare.
I took mine out and shortened the end about 3/16". I posted about this, but I didn't save it and haven't been able to find it. it changed the light cutoff and now puts more light on the road.