I have no involvement in the design process and I never even look at the PSDs, but I did ask Mike about it, and this is the answer I got:
Those are the only images in the design and the rest is strictly CSS, so items that are CSS only don't need to be in a PSD.
The PSD is set up for slicing so users can change the graphics and simply re-slice them if they want to change something.
Anything else is CSS and would need to be modified in the CSS code, not an image or PSD.
While it may not exactly be optimal, you can always slice "screenshot.png" from the theme folder and use that as your basis for any design tweaks that you feel need a visual representation.