Cloud storage takes care of all that. People seem to forget the iPad does come with internal storage so you CAN actually store things on it
You are not wrong.
But, this is what Apple always does -- they pick the one way that they think is the future, cut everything else out, and expect us to line up and adapt.
And if you choose to live in a 100% Apple ecosystem, then hey, it works great! It makes perfect sense. If I buy all my music and movies from iTunes, then why would I need to store them anywhere? They came in off the cloud in the first place, of course I can just download them to my iPad.
And if I take all my photos with that (awesome?) iPhone camera, then I'm all set!
But for those of us who rip our own music, convert (or make!) our own movies, take photos with a real camera, or deal in an office environment where the files we want to touch are not always solely created by ourselves, we need to jump through hoops.
If I want to shoot video clips with an actual camera -- not an iPhone or iPad -- how do I import the photos and video? I can't. Oh, well, I can, with the CCK. That is apparently Apple's only concession that, yes, sometimes you DO want to be able to plug in an external device.
Part of the beauty of a device like an iPad is you can use it away from networks, away from the internet, away from the cloud. The cloud is a great thing but until it is 100% ubiquitous, world-wide, then there is no disadvantage to offering other options.