I'm guessing he is giving this warning to those that routinely set their phone down in public places. Say a restaurant or bar table. Mass transit, Uber, Lyft, and taxi's come to mind along with the way they make pockets now. Your damn phone falls out every time and you don't know where that back seat has been. Just saying. Depending on your commute, it doesn't hurt to wipe down your phone if you want to. Now if you are taking your phone apart and yelling "EVERYTHING MUST BE CLEAN!". Then you might have overreacted.