It's not just cellphones we throw away when we have no further use for them; it's the chargers that come with them. The companies who make cellphones - and arguably Apple in particular - are to blame for this. At an earlier stage of cellphone development, most different models of phone used the same charger. Now, each manufacturer tends to demand the exclusive use of chargers supplied by them. That means old ones are thrown away when new phones are released.
We don't help with this either. We treat phone chargers as disposable. Left your charger at a friend's house? Buy a new one. Can't remember where you put it? Buy a new one. Worried about losing one? Buy two or three backups, all of which are useless when you come to upgrade. You're looking at the net result of all that disposability; a mountain of phone chargers that will never degrade, and yet will never be any use to anybody ever again.