As an unhappy Surface user, I applaud Apple's ability to recognize that a tablet and a "computer" (be it laptop or desktop) are fundamentally different usage scenarios that the same hardware and/or OS are unlikely to satisfy without compromising and making both experiences less optimal.
For the record, you can in fact hook a USB keyboard up to iPad (and even iPhone). Bluetooth also works if you prefer wireless. The devices don't have standard USB ports, but an $8 adapter (http://www.amazon.com/dp/B00HPQUBGK) works nicely if you prefer wires. On occasions that I plan to do major writing while traveling, I'll bring a BT keyboard along. I always have the adapter with me in case something sneaks up. I can just "borrow" a standard USB keyboard from somewhere and type up War & Peace on the go...
iOS can also do some (very) limited things in terms of USB storage with one of those adapters, but it's pretty much limited to dumping photos to/from a memory card. General purpose USB storage capabilities might be nice sometimes, but they've never been the thing that made me pick up my Surface instead of my iPad.
About the only win on the Surface is the proper stylus which makes handwritten note taking much better. Haven't had a chance to try out Apple's new stylus thing on the iPad Pro yet. Very much hoping they bring it to the next iPad-normal revision as the extra size of the Pro is almost as much of a DO NOT WANT for me as the oversized iPhone 6 line.