Why can’t we recover precious metals from landfills?

Mining for precious metals like gold, silver, and copper is extremely costly. Not only does it require a huge amount of energy and have a devastating impact on the environment, it also puts human life at risk. Still, these metals are what enable our precious smartphones and tablets to work so efficiently, so we have to get them from somewhere. But what if that somewhere was old gadgets we no longer want instead of deep within the Earth?