I think they are being dishonest about their "bafflement" over the persistence of DVDs. I think the real reason is the quality of their streaming collection. There a few gems but it is filled with a lot of sub-par, unwanted, titles. I for example, have watched all the streaming videos I want for a while. Now I am just waiting for the new ones to appear and watching real DVDs I get in the mail.
But to give them the benefit of the doubt, it would be interesting to see how they determined that streaming just isn't that popular. They could have judged by the total # of subscribers that have ever setup or watched a streaming title? The best way would be if they focused on titles offered both in streaming and non-streaming form, then investigated which form people actually choose.