I'm grateful for all the requests I've gotten about this. The short answer is it would cause fulfillment to take much longer.
The long answer is that the portfolios are my hand-picked favorite collections of prints from different categories. They're offered here at an extreme discount as a thank you to backers. If I offered every print on my website as a choice, then the shipping process would take much longer, coordinating which prints went with exactly which order, and having to find and adjust files for best quality. I'm a perfectionist, but mistakes would be made and I want to give you the best I can.
None of this means we won't offer more portfolio's when the final surveys go out, but for right now we're focusing on the layout of the book.