I can only guess that they have some other major business change planned but as of yet unannounced.
This is pure conjecture, but spinning off the DVD business would be the first step in making it easier to sell off. I recall some articles a while back that talked about how much more profitable the streaming business is than the DVD business. With that in mind, this is somewhat plausible (perhaps in the future if not immediate).
I’ve got a couple of streaming movies to watch before I plan to cancel my streaming account. I was thinking I’d keep an eye on things and maybe re-enable it in the future when my daughter is a little older, but the split into two services sounds like it will make future account changes like this more awkward.
Related: Chuck & Beans.