If you forget to do so, a new user can never use it
You might get bored with using your old phones and that becomes the reason to sell it to someone else who is looking for it. Of course, several other reasons are also there, in case your phone got damaged and you are not able to use it that time too you think about changing it. But that is a different reason altogether. If the condition of your phone is good but you are planning to change it for a new one, never forget to put it on “Factory Reset”.
Why? I will tell you the reason now.
You must know it is the “activation lock” that saves your iPhone from getting lost. Since no one other than you can access the data of your phone you can easily find it out if you ever lose it or it gets stolen.
It is this activation lock system prevents the new user from using the phone even if you sell it. This is the only reason why usable phones are junked up each year for the recycling process. Recycling is a good idea than just thrashing it away and making the world more polluted. But if good phones can be used again rather than recycling them then, that’s the best thing can be done.
U.S Company Wireless Alliance has been in the business of collecting old smartphones for the purpose of reselling or even recycling and till date, they collected above 6 million phones through donation boxes either at schools, churches or across various businesses. But, if someone forgot to turn off the activation lock that phone becomes useless.
But never get confused between activation lock and your phone’s passcode. If you turn on the activation lock it will be linked with your iCloud account through your Apple Id and Password. So, even if your phone gets stolen it is possible to detect through iCloud account and also you can delete all your relevant information from there. Unless the activation code is deactivated its ownership will never get transferred.
Since the activation code doesn’t appear on the interface like a passcode, people have a tendency of forgetting about it while giving it away. But again, it is highly recommendable to put the phone on factory settings so that the phone’s activation lock is disabled.