This is my boyfriend exactly. I have come to believe he truly just does not see or it just does not register that there are crumbs all over the counter and egg drips all over the stove after he makes breakfast. He is much more of a slob than I am, and I knew that when we decided to buy a house together. I am "training" him and he is trying. Just getting him to remember to recycle is a battle being won slowly, but surely. I still have to pick through the recycle bins to throw away plastic that can't be recycled - I do have him checking for the recycle symbol on the back and it is working about 50% of the time, but that is major progress compared to when he lived alone (he never recycled anything)!
My other pet peeve is the crud that is left in the sink drainer thingy - I am of the practice that when one cleans up the kitchen after a meal, that includes getting the little food bits out that cling to the strainer at the bottom of the sink; if you don't, they just dry up and clog the filter and then the water stops draining!
My theory is that in his work life he has to concentrate very hard on detailed lines of computer code, so when he comes home, his brain is just too tired to register the kind of details like crumbs and spills. And in his defense he does a lot around the house that I cannot do at this point because of my bad wrists - he chops the wood, fills up the cistern, changes the propane tank, etc. It all evens out in the end anyway; I keep the kitchen and bathroom clean, and do most of the vacuuming. We trade on doing the dishes - if one cooks, the other does the clean up. There have only been a few times that I feel a little aggravated about something and I will tell him and he does try to change, but it is sometimes like pulling teeth to get someone to change a long-standing habit. All in all, he is such a keeper in all other respects and we are still having fun making a home together after these first five months!