Perhaps all of those things are true. A guy can still be curious.band what about more powerful iPads?There's a very good reason.
Perhaps it's the new camera itself, perhaps A9 makes it possible, perhaps additional RAM helps with the live capture, perhaps another tent pole feature was needed for the marquee. Any and all of those are legitimate reasons, none of which you "need" as a consumer.
Can't blame people for being cynical. On the surface it looks like s feature Apple wants to restrict to newer devices to get you to buy them. Without an explanation as to why, we don't even know that's NOT the case.