Macs, iPhones and ther electronic devices contain precious minerals such as cobalt, lithium, copper, silver, platinum, tantalum, tin, tungsten and gold.
The reason behind such laws is not merely for environmental conservation, but also due to social concerns. In many states in the US, it is illegal to dispose of electronic waste without sending them to a proper disposal facility. Although we are a developed nation, our recycling efforts are far behind other developed nations. Singapore is the largest producer of electronic waste in Southeast Asia.