What would you think if a business sells their products only through one retailer? Economic suicide! Isn’t it? Why sell books only to one company? And it is not even selling, it is a kind of consignment… as they don’t pay you upfront, only when your book is sold, will you get money!
Authors would be wise to sell their books not only through Amazon but as well on Barnes & Noble, Apple and especially Kobo and other online book retailer websites, to have their “eggs in more than one basket”. Either directly or with the help of one or more international distributors – who also can distribute it to libraries and the independent bookstores.
If you go the indie route and choose for example the POD services and worldwide distribution through Draft2Digital, IngramSpark, eBookPartnership, or Lightning Source (provided you have at least ten books to be considered a small publisher by LightningSource) your book is printed on demand and will never get discarded (good: no-return-policy in POD worldwide distribution). See these articles “How to Distribute Your Book Worldwide” and “How to Sell Translated German-Language Books Overseas”.