There are two kinds of EPUB files—reflowable and Fixed Format. Keeping page numbers in Fixed Format makes sense but doesn't make sense in reflowable. Ebook readers can usually let you change the font size, and sometimes the orientation of the page so there is no fixed page numbering.
As to DPS, you should ask in the DPS forum:
I wonder if you are referring to what is called in EPUB "the page-list"?
This is extra metadata/navigation built into the EPUB document which provides a way for a user (depending on how the device/browser/reader supports it) to see what PHYSICAL page some content was on.
The "page" it is on in the reflowable EPUB is of course no relation to the original document page, which is why this support was invented.
Have I guessed right?
Architect, InDesign Engineering
Ps. We do not yet support any way to author/export the "page-list" from InDesign CC.