This decision was not made over night, and this change has been coming for quite a while. In fact, if you go look at this post on Netflix's API blog dated 27 June 2011[1], you'll see:

As of Oct. 14th, 2011, the Netflix API will be focused exclusively on offering content and functionality from the streaming catalog. As a result, we will be discontinuing the support of DVD-related features in the Open API.

They go on to say that this is to support long term goals around internationalization, but that does not, by any means, preclude this split.

[1] http://developer.netflix.com/blog/read/Upcoming_Changes_to_t...