why should amazon bother - as things are, you are incentivised to by a proper kindle reader, which suits them ( the preferences within Kindle for PC/ Mac.. are even more limited )
you should also be aware that to use the kindle android app, you are logged into your amazon account with 1 click digital purchasing unavoidably on- so 1 misjudged tap will buy the matching audio book as you cannot suppress the in-app banner offering for that
. and a similar blunder in the prime video android app can saddle you with an expensive and not-returnable movie. proper purchase/parental controls only work on amazon hardware.