Even with full USB OTG support a separate adapter would be required to connect USB devices with standard-A type plugs. This makes USB OTG largely useless for use cases like quickly needing to copy a file from a friend's hard drive or USB stick, unless you're always willing to carry an adapter with you. And I don't like the idea of having a highly-integrated pocket-sized mobile device and then having to carry a bag of accessories with you. The moment you can't fit all the stuff in your pocket you're better off with a larger device anyway