Why do lightbulbs need to be recycled?

The components used to make lightbulbs, primarily glass, metal, and phosphorus powder are recyclable and when managed properly, can be recycled into raw materials for manufacturing.  While incandescent and LED bulbs pose no danger to the environment, more than 2 billion lightbulbs are used every day in the U.S. (the average home uses 40), so the opportunity for material recovery and landfill diversion is significant.