Anecdotally, my experience is the exact opposite. Since Netflix does not attempt to sell devices (like Kindles, for instance) itself, their streaming app is on literally every device I own that is capable of running it.
Lots of Amazon streaming apps (off the top of my head, the TiVo app) only support normally purchased content, not the free Prime streaming; and other platforms (say, Chromecast) don't have apps because (I'd assume) they likely don't fit into the ecosystem that Amazon wants you to exist in - namely, Kindle-based devices.
In other words, I'm actually considering dropping Prime because (among other reasons) Amazon's attempts to push related products and systems reduces the utility I can get out of Prime Instant Video.
Lots of Amazon streaming apps (off the top of my head, the TiVo app) only support normally purchased content, not the free Prime streaming; and other platforms (say, Chromecast) don't have apps because (I'd assume) they likely don't fit into the ecosystem that Amazon wants you to exist in - namely, Kindle-based devices.
In other words, I'm actually considering dropping Prime because (among other reasons) Amazon's attempts to push related products and systems reduces the utility I can get out of Prime Instant Video.