If the Apple Watch has wireless charging, why doesn't the iPhone?

For years Apple has been accused of ignoring, or stubbornly refusing to add, wireless charging on the iPhone. Since the Apple Watch uses wireless charging, and uses it exclusively, Apple is certainly both aware of the technology and willing to use it where the company thinks it makes sense. So, why doesn't Apple use it for the iPhone?

In a word, "physics".

Up until recently, it wasn't possible to use wireless charging—also known as inductive charging—on devices with metal casings. That's why the Apple Watch has a ceramic back.

The iPhone, by contrast, switched from the glass backs used on the iPhone 4 and iPhone 4s models to the aluminum of the iPone 5 and subsequent models. That meant, at the time, Apple couldn't have both aluminum and wireless charging.

This year, that changed. Last July, Qualcomm announced technology that enables wireless charging on phones with metal casings.

That was too late for inclusion in the iPhone 6s but the iPhone 7 is just over a year away, and more iPhones beyond that.

Who knows what they future holds?