The point isn't really for the FS alone to save you from a hardware failure, it's that there are failure modes in which you won't even know that a failure happened unless something is hashing the data on a regular basis. It doesn't have to be the filesystem, but that's arguably a reasonable place to do it (and ZFS is really more like a combination of filesystem/volume management/softraid than just a FS anyway).
Crazycheese, your poor grammar leads me to think that you are from a non-english speaking region. I'm from australia, but i'm aware that in america (as per your example) there is legal precedent to indicate that if you develop parts for a purpose (such as a nuclear reactor) and they have a failure, then you can be at fault for negligence. From memory the precedent was kind-of set by a case involving buick and some wheel manufacturer.
Also, it might be useful for you to think about what a filesystem is. It's a component that is used by the computer to reliably read and write information in a persistent way. Hardware failures might cause the filesystem to work incorrectly, but the file-system can very feasibly be improved to get around a lot of problems.