The Android smartphone charging protocol is a bit of a mess. While Google itself has been using USB Power Delivery protocol since last year to provide fast charging on its devices, most Android devices rely on Qualcomm's Quick Charge, while others have come up with their own version, such as the DASH charging on the OnePlus 3.
Unfortunately, both of these are proprietary solutions and require a specific piece of hardware on the device/charger/cable, licensing, as well as messing around with the standard USB power delivery protocols. It also makes them incompatible with desktop or notebook computers that have USB PD charging and thus makes them charge slowly.
Google doesn't seem too keen on this, which is why the company has added the following in the Android 7.0 Compatibility Definition, that all OEMs have to adhere to if they want access to Google's proprietary apps.
Type-C devices are STRONGLY RECOMMENDED to not support proprietary charging methods that modify Vbus voltage beyond default levels, or alter sink/source roles as such may result in interoperability issues with the chargers or devices that support the standard USB Power Delivery methods. While this is called out as "STRONGLY RECOMMENDED", in future Android versions we might REQUIRE all type-C devices to support full interoperability with standard type-C chargers.
Why is this important? Think of it this way, in future you can just carry one charger for your laptop and your smartphone or any other device you might have. All of them will connect with USB-C and because they all support USB Power Deliver they will all fast charge from the same charger. This is really the point of having a unified interface such as USB-C and as long as manufacturers keep using proprietary solutions that only work with that particular device this future will forever remain a dream.
It looks like a Nexus 6P my friend.
Prasad is right, iphone charging is a mess,, earphones charging, dongle, just chaos, and inconvenience, perhaps they will learn from android again and clear up the tangle.
Sounds selfish at first, but Google has a point. In order to for USB-C to minimize the mess, vendors should adhere to the USB spec to maximize compatibility with external peripherals. External devices use the USB spec anyway.