I'm not quite sure what you mean there. Your software certainly should do regular scrubs, but there are a lot of storage systems out there that don't do this. And there most definitely are SSDs that do their own scrub akin to what host software can do.

Yes. The combination of erasure coding plus regular scrubbing is already the standard in the largest proprietary storage systems. As it happens, I worked on exactly the scrubbing piece ("anti entropy") for such a system at Facebook. There was a lot of analysis of data-loss probabilities based on encodings, placement across power/network domains, scrub rates, repair rates, etc. Since there are also performance and resource-use implications behind many of these, it's actually a very complex balancing act. That's why the knowledge of these second- or third-order problems and their solutions is slowly filtering down to storage systems you can deploy yourself.