Okay, so here's the thing. SMART apps are on multiple types of devices such as TV's, Blu-Ray Players, Gaming Consoles and SMARTPhones, none of which Amazon makes. For this reason they don't have anything to lose putting the streaming app on them. They do however have much to lose putting their app on TV and Google's Chromecast since Amazon makes a major competing product. Why are you making this only about Apple and not including Google? The article does mention Google.
Amazon may have less to lose, but not nothing to lose. They do make the Amazon Fire Phone, as well as tablets and the Fire TV gaming console. So, they do compete against other manufacturers in hardware and still provide their apps and digital content for sale.
And I didn't mean to make this only about Apple. I have very little experience with or knowledge of Google products, so I was speaking from where I have the most experience.