Not all streaming providers do this. For example, if you buy a movie on Apple TV, you can download it. To me, that makes good on the "buy" agreement. Based on my last experience, I was trying to buy a movie that was available both on Amazon and Apple for the same price. The amazon version is bound by the EULA, and they don't let me download or play on non-DRM protected devices/apps. But Apple's was good. So I don't buy movies on amazon anymore.