Piracy is just the excuse. What they're saying is that Amazon will allow a collection of corporations (including Amazon) to decide what you're allowed to do with the hardware they pretended to let you buy.
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But you can't get the same subscription with movies/TV shows. You get a fraction of content with each subscription. When there will be a reasonably priced subscription for most of the video content - it will change the situation.
So in my opinion, it's not about DRM. It's about convenience.