Kindle does that because you can change the font size and switch between devices and the pages wouldn't be the same. Say on a Kindle with medium font you can view 300 words on a page. If you change to the large font, now you only see 100 words on a page. A book that started with 275 pages, now has 825. And then when I sync to my Android phone, I can only see 60 words on a page.
Page number wouldn't mean anything in this case. I would rather see % complete although many people think otherwise.
Amazon came up with the numbering system so you could find the same page. I'm not sure where they come up with the total number (maybe based on the number of words or lines or whatever), but each page is worth a certain number of 'places'. Read this guy's explanation of it:
http://www.edukindle.com/2008/08/pag...ion-on-kindle/