My best guess as to why they are splitting the queues is due to the availability issues on the streaming side affecting customer 'morale', so to speak. i.e. when a streaming-only customer searches for a title, and then finds that it is only available on DVD, their perception of the service is diminished.
I think the end goal of this move is to kill off or sell the DVD portion of the service entirely, so by splitting the services, investors won't freak out when that eventually happens. This also is another reason for splitting the queues.
That is the main reason why I want a unified queue: inconsistent availability. I put "Scarface" on my queue, but being a low priority it's pretty far down; I was content that someday it would reach the top of the DVD queue and show up, or that on a whim I could hit "Play Now" and stream it. One day I noticed it was tagged for removal from streaming a few days hence, and didn't have time to watch it in the meantime. Streaming option disappeared. [shrug] Well, it's still available by DVD, I'll get to it. Then I get the "we're going to split the service" notice, note that I only watch 2-3 discs a month (lots of streaming instead) so the separate fee wasn't worth it and I canceled. Even if I want to pay a one-time rental to watch it, not available as an option and alternatives (sign up, get disc, cancel) are too much hassle now.
Huh, maybe I'll check Amazon, where I can buy "Scarface" new, buy it used, no-strings streaming rental, or maybe even Prime "free" streaming...and all from a single search...[clickety clickety]...ah, it's $3 to stream it once, and there's 53 purchasing/renting options from $0.01+shipping used VHS to $3 streaming rental to $700 including humidor. Pity it's not in the "free Prime streaming" option, but at least I know the options with one search.
When I put something in my DVD queue, it automatically appears in my streaming queue when it's available. This makes me happy, I watch the movie online, then delete it from my DVD queue. If the new system no longer supports this, it will affect my morale.
But I suspect you're right about killing off or selling the DVD service, and I think they're intentionally trying to sour customer opinion to bring about this end. It's a shame, because Netflix, as it previously existed, was one of the few subscription services I was happy to pay for. After the site redesign, everything's gone to hell (instantwatcher.com is the only useable interface I've found, on any platform). Oh, well, it was good while it lasted...
I am getting the feeling that Netflix's customer base doesn't understand why some titles are available on streaming vs DVD only (this is based on random comment reading). It is a very subtle difference, but it comes down to 'Netflix doesn't have the title' vs 'Netflix has the title but they won't let me stream it'.
Admittedly, the much bigger motive is that they want to get rid of their dvd-by-mail business.
I think the end goal of this move is to kill off or sell the DVD portion of the service entirely, so by splitting the services, investors won't freak out when that eventually happens. This also is another reason for splitting the queues.