It offers easy scaling, great stability and reliability, works across many different environments. In short, it offers all the features that developers love.
The fact that it doesn’t exist — there isn’t anything that could be appropriately called a storage architecture in Kubernetes.
This would incorporate Google’s and Red Hat’s particular design bias into the system, and it would contribute to vendor lock-in, something that would be against the open source nature of the Kubernetes project.
Ultimately, all this is to say that commercial storage solutions are a better fit for most Kubernetes users than open source ones, but that doesn’t mean you can skip the evaluation process.