They're assuming that everyone has cheap, reliable, easily available broadband. Whether it be for movies, operating system downloads, or just everyday use, this is a patently false assumption. When the floppy was killed, DVD/CD media was an immediately available replacement for many, if not all users simply by visiting their local store. In this case, users are at the behest of other companies who do not have a financial incentive to provide service to many areas - let alone ensure reliability or access.
This is before we even mention the picture & sound quality or the constant "rebuffering" waits. Yes, all you lovely people who loudly proclaim the death of physical media for downloading - many of us envy your ability to make that change. And before someone says "Well move to somewhere that it's available", I live in a major metropolitan area, top 25 DMA. The internet service sucks due to poor infrastructure, regardless of who you subscribe to. And let's not forget bandwidth caps.
Downloading/streaming only is not yet a viable permanent solution.