They haven't invested enough because they think technology as it is is "good enough".
And it is true... problem is, the moment you stop investing you product starts being a commodity. And that means low margins.
Disk cabins may seem as great for admins, but from my point of view, they are very VERY expensive in terms of lost time in latency.
The very same people that defend this kind of storage are, in my point of view, the same ppl who said flash storage was wrong.
Storage belongs INSIDE the server, as close as possible to the processor for most loads.
That of course, would mean treating the servers as "compute units", and you would need different tools to manage servers, loads, etc. More easy to say than to do, of course....