I can understand not dragging self-deleted content into the spotlight. If there were problems with it, it's deleted anyway and they don't matter now, and the OP probably had their own private reasons for deleting it. Nothing wrong with self-deleting answers if you know they're bad.
But why are self-undeletions not shown? Seems like it'd be pretty easy to abuse; it's the only way to (re-) introduce posts to the site without anyone noticing. I can think of two scenarios off the top of my head:
A frustrated user abusing the moderators. Downvotes and flags start to roll in? Simply delete it to dismiss the flags on it and undelete later. I've actually seen this one happen before, but it was re-deleted fairly quickly because it was still on the front page.
A spam bot specifically designed for Stack Exchange. Post spam to a high-view question, immediately delete it, undelete it after a week or two when nobody's going to notice.
Is there a specific reason for not showing these posts to 10k users?