One problem is that even though your old phone and new phone might both use the same connector for charging whether that be Micro USB, USB-C or Apple Lightening. There is no option when buying a new device to say you don't require a new PSU and cable as you already have one, as they are usually bundled inside the box with the device. And therefore you end up with several chargers all the same. I have 2 that are surplus to requirement now and are just collecting dust in a drawer as they are not even worth selling on ebay due to their low resale value.
But on another note there are a few different manufacturers using incompatible fast charging power supplies which if you don't use their specific charger you will only get slow charging even if the physical connector (USB-C) is the same.
Biting the hand that feeds IT
