Western Digital is a big supporter of RISC-V because they (probably) plan to replace the Marvell MIPS chips in the HDD devices with RISC-V.

But the reason you probably don't get storage superstars is because it's a healthy market. There are only a handful of cpu manufacturers/designers (amd, intel, Nvidia, apple, Marvell, ARM, Qualcomm) and because the instruction sets are not compatible it's a huge undertaking to move to a new architecture. All applications must migrate.

But with storage the application uses POSIX and you can out any hardware behind it. Or object API. Or a db. But mostly the application doesn't care except in very precise cases where performance matters a great deal. And even if one application needs object and another is ok with a posix API, it's ok because you can use both from the same machine. So the choices aren't as dramatic.