This whole topic is one that really frustrates me.
I've recently moved from Android to Apple. Hey, Apple is for creative folk, right? But it seems that the product managers in Apple have never really worked with any kind of photographer in their lives.
All I would want to do is plug in my camera or a card reader and copy images off a card onto the iPad memory. Then remove the card, and plug in a portable hard drive with its own power source. Finally copy the images off the iPad and onto that hard drive (probably repeating this for a second hard drive) before deleting them from the iPad.
There is nothing in this that an iPad couldn't do, but Apple clearly doesn't want its customers to be able to do that.
To be fair, it would cost Apple money to do that in terms of testing and verifying it every release and support calls on something that some customers might find complicated. But it would make it into a heck of a useful thing for travel / holiday photographers.
I know that some will say that iCloud should do everything you need, but they probably haven't tried to working in a remote hotel with dodgy wifi, or had to pay to upload multiple gigabytes of RAW files over pay-by-megabyte international cellphone connections.
Sadly, I don't think that we are a big enough group of people to interest Apple.