As a book publisher and photographer perhaps I can offer a different view. First off let me say that I agree about the way that most two-page spreads are published - ruins the image for sure and I can't believe how often this is done. But this fact is all about the design person being an idiot or knowing nothing about composition or how the book is printed and put together - I'll get to that in a moment.
I'm putting the finishing touches this week on the eighth coffee-table picture book of my images , and it includes 11 "double-truck" spreads (I prefer to do my own design instead of letting someone else do it so that I have total control of the final product). It has nothing to do with money - the cost is exactly the same. It has everything to do with my personal desire to show the image larger, that's all. When you create some works of art there is often a great deal of fine detail in parts of the image that you simply cannot see well enough when it is only enlarged to a single page. Putting it across two pages simply allows the reader to view the detail better. Of course, you generally have to have great image quality in the first place, otherwise it will look bad. However I once knew an editor at National Geographic who told me "If it is a weak image make it BIG!" I guess the idea was that something large would have such a positive impact that the poor quality would be overlooked - something I do not agree with. The image has to be better than the rest first.
You can't just slap any old image across two pages and expect it to work - one mistake the design folks make all the time. The composition and subject matter has to work first. What I do is look for images that have interesting composition on either side of the image, generally looking in at each other, and with no important info in the "gutter" (that is the fold where you lose a bit of the image). What I see most designers doing is simply looking at a double-truck spread without taking that gutter into consideration, and more often than not they put the most important part of the image in the gutter (probably shouldn't be in the middle of an image anyway).
The second mistake they make is that they don't have a clue where in the book to place these two-page spreads. You see, a book is printed on large sheets of paper called "signatures" that contain 8, 12, 16 or more pages on each sheet. Once both sides of each sheet are printed, that sheet is folded and eventually trimmed. There are only two pages on any single signature where you can place a two-page spread without the picture being cut in two (or printed on two different parts of the sheet that are not together), and unless you place the image there you are asking for trouble (the two sides not lining up or the color being different). It is possible that the two sides of a single image might even be on two different signatures if not placed correctly. It is just simple math - all you have to do is divide the number of pages in a signature in half and that is where you put your image - a 12-page sig for instance would have a "crossover" on pages 6-7 - i.e. a photo placed across those two pages will remain intact when the book is printed, trimmed, and bound, but no other pages on that sig will be. In fact you can open up the book and lay it flat and you will see one complete image, nice and big. I continue to be stunned how many picture books don't follow this simple rule. For me, heck I begin the entire book design process by asking "how many pages are going to be in a signature?" Then I select and place those crossover images first and build the rest of my design around them.
By the way, pattern images with no central subject make terrific double-truck images, and printing them larger really can make them pop.
So YES, a lot of the images you see published in picture books look like crap - because the designer choose the wrong image to place there, and/or put it in the wrong place to begin with on the signature.
And also YES, some images look just terrific and can add a great deal to the enjoyment of the reader if done correctly.
It has nothing to do with money.
One last thought - I've seen editors make images too small much more often - when even bother to create a fine work of art if they are going make it the side of a postage stamp where quality does not matter! Another reason why I have always published my own books (plus I get to keep all the profits). And all of my books contain ample white space too...
Tim Ernst in Arkansaswww.Cloudland.net