Performance is only an issue if your disk can write faster than your CPU can hash. hammer2 changed its hash a couple of years ago because this started happening with newer NVMe drives[0], but before that disk writes weren't CPU-bound.
What about:
* Disk reads may unnecessarily trash the CPU caches, because CPU will need to verify the checksum when the DMA read is done, even if the app isn't going to process the data immediately afterwards
* Battery life - without checksums the CPU can stay mostly idle, and go into a lower power mode, while the disk controller does its job
[0] http://lists.dragonflybsd.org/pipermail/commits/2016-June/50...