Just curious: Kindle Magazines

I can buy a book on Amazon, download it directly from Amazon to my iPad, then read it with the Kindle app. It works fine. When I try do to the same with a magazine, however, I get this message on the Amazon site: "magazines are only available for Amazon Kindle devices". Why is it not possible to download magazines from Amazon and read them on the iPad? Something to do with the formatting / file type? Thanks