Just to expand on this a little bit, from my personal perspective.
When you produce the deck with USPCC, they have many many gross of them in their warehouse once the deck is done. Several of the resellers are actually within a short drive of the USPCC factory so they can actually just drive over and pick up the decks that they paid for, eliminating the need to ship extra things around. For other resellers, USPCC ships them their decks direct. USPCC then puts the rest on a freight truck and drives them to the designer. Usually, the resellers see the deck before the person that made it!
At that point, the resellers have their decks and many years of structure sending stuff out. The independent designer generally does not. So we have to coordinate the Kickstarter backers lists, the survey results, incorporate any special requests and deal with other outside orders. We have to order rooms full of shipping supplies. Order postage, print labels, make sure each order gets the right thing, sign hundreds of uncut sheets and decks, etc etc etc.
Not to excuse long shipping times, but ordering a deck of cards from the guy that made it is a very different transaction than ordering a book from Amazon. Speaking for myself, I've put in days of effort on working out shipping alone and hope to make that a very efficient process but even then, doing any detailed task 1000+ times is a lot of effort and takes time. My goal is to get everything out, en masse, from 1 deck to 144 decks so that I don't have to worry about it anymore.
I'd love to have made my deck, had them in hand and then just sold them but the finances to do that are out of my league, so we all have to deal with some of the unfortunate byproducts of Kickstarters model. I think that things will get better and more efficient as time goes on. I know that my next effort will be far simpler to deal with, because I know the routine. Just like anything in life, the first efforts are the hardest.