D.,
I, too, am really interested in the psychology of this. If you get any responses from anyone with insight as to what is going on in his brain, please let me know. My husband is exactly the same. From where I'm sitting, I see the graham crackers he was snacking on last night, the bottle of aspirin he brought downstairs to take a couple, his high school yearbook he took out to "look someone up," etc., etc. Nothing ever goes back where it came from when he's taken it out and the next time he wants it it's always "where did you put my . . .," generally in a pretty snotty tone. If I can't immediately produce whatever "it" is, somehow that's my fault.
My own thoughts on the subject are that we came from two completely different backgrounds as kids. He was raised by a working single mom in a small house with six kids. It was complete chaos all the time. I was raised by a stay at home mom in a small but very orderly home. What you learn as a child, you become as an adult is my theory on the whole thing. And once that behavior is learned, it's very difficult to change.
My one small victory is that I have solved the mail problem by immediately recycling the junk and filing the bills and important stuff myself. He has a mail slot for things that pertain to him only. He still lets that stack up, but eventually he grabs the whole pile and takes it to his office. The pile was originally on the mantle where he liked it, but I moved it to the cubby near the back door. I took some heat for that for awhile, but he doesn't mention it anymore.
To TwinMama, our dishwasher gets unloaded in exactly the same way! To his credit, he does put the dirty dishes in, but the clean ones are just piled on the counter.
Great post, D.. Good luck!