Streaming has a unique disadvantage: you have to haggle with each individual content owner.
Yes, it's cheaper to move bits than stuff. Much. But licensing is a pricey hassle. It's a huge part of the comparison, and as content owners get savvy, it will only get more expensive over time.
This should be a signal of how much more right we got the law with physical media. We all want DVDs to be dead, sure. But DVDs would die tomorrow if we just set up an obligatory licensing scheme for this sort of content. If you distribute a movie, Netflix should be allowed to stream it, and pay you a fair statutory fee.
(This isn't some a radical new idea or some Communist scheme, it's basically how radio stations work.)
Until the law is fixed, DVDs will stick around, lingering on.