It would be stupid to throw away the old iPhone instead of selling it or giving it to someone. Who does that? If people are actually doing that, which I doubt, then it's not Apple's fault.
Besides, do you know how TINY a phone is? It's such an insignificant amount of waste (for those people who supposedly throw away iPhones) when you consider everything else someone would throw away.
the phone itself is not the source. its the manufacturing waste that goes into it that is the problem. its like EV cars. "oh, im not burning gas! im so green!" but they're not thinking of how much pollution was generated in making those batteries.