I completely understand and share many of your fears, even though I will likely buy the PS4K day one. My negative outlook is more on the future repercussions and ramifications of this strategy, which I feel are less consumer friendly, and offer less value proposition per hardware cycle.
To answer your question, I think the reason Sony would risk it is not only to better enable the PSVR, but also to try it's hand at a release cycle that more closely resembles other technologies, simply because it has the potential to be more profitable for them. More hardware revisions, shorter cycles, less subsidisation, more crossover etc. Not sure yet if it will pay off, but we shall see. They certainly also have the potential here to squander a lot of their goodwill, and make consumers feel somewhat less confident in console purchases going forward.