Benefits to Apple
Apple is known to maintain one of the best managed supply-chains in the world. Using its large-size and global presence, it is able to demand high quality and impose stricter terms on its suppliers. For example, when taptic engines from a Chinese supplier proved unreliable, Apple swiftly procured them from the Japanese firm Nidec Corp (mentioned earlier). Apple has hundreds of such suppliers willing to abide by the terms Apple sets forth.
And outsourcing its component production and device assembly allows Apple to do what it does best – concentrate on designing great products that offer rich functionality and are easy-to-use. (For more, see: The Apple Ecosystem.)