I think you misread/misinterpreted. I didn't say there were epubs in the kindle store, but that many of their ebooks were converted from epub format [to get them into the kindle store as kf8 or mobi]. To elaborate: You can't natively edit kf8 or mobi files (at least not with mainstream editors). kf8 and mobi ebooks therefore originate as html or epub (which are pretty much the same thing, ignoring that epubs are zipped, and ignoring simple extras like toc and cover page semantics). Kindle-supported kf8 format is generated using kindlegen operating on either a epub or html source (or some other formats, which aren't recommended because they lack formatting parity with epub/kf8). The point being, ebooks are basically in some quasi-html open format to begin with, Amazon requires converting them to a proprietary format (and kf8 is a very thin proprietary veneer over epub) to get them onto kindles... a conversion that serves no practical, functional purpose.