Apple has used the lightning connector for seven years. It used to be on everything, but now it's only found on two types of devices — iPhones and some iPad models. The lightning cable Apple includes with the iPhone doesn't support fast charging and transfers data at USB 2.0 speeds. Switching the iPhone to USB-C could unify Apple's products. 1. It's proprietary - so fewer devices can use it. 2. It's more expensive. 3. It's slower. 4. It doesn't support fast-charging.