You know, hardware isn't free, right? Each Kindle model requires R&D, design, testing, manufacturing, lots of work to product, beyond the ability to show books. Sure Amazon makes money off the books, too, but those files aren't free to store on a server (and the servers aren't free), or free to send to you over the Internet, and so on. Ads support hardware cost. If you don't want to see ads, buy the one without ads.