There are other reasons for doing this. Even if Kindle market would function forever and Amazon won't delete books remotely there is still a possibility that yo

There are other reasons for doing this. Even if Kindle market would function forever and Amazon won't delete books remotely there is still a possibility that your account could be breached, for example by social engineering means. And if malicious person can access your account he can delete everything there, forever. If someone will steal your Steam account you can restore it completely, most likely. If Amazon acc is stolen - goodbye everything. And support won't restore or refund anything. (support itself is good)