There is also the issue that lower abstractions don't always give enough info to higher level extractions, and vice-versa. Take OS filesystem code for example.

There is also the issue that lower abstractions don't always give enough info to higher level extractions, and vice-versa. Take OS filesystem code for example. It would be useful for the low level storage driver to have info that the higher level FS possesses so it can tell the hardware that certain blocks of storage can go back into the write leveling pool (i.e., when a file gets deleted). Or, the other way around, the filesystem driver can make better file allocation and access patterns if it knows that the minimum write size for a block on an SSD is 128KB, or that starting a write on one block, and ending on another, gives better performance if that first block is picked to be on a stripe boundary on a RAID drive.