Why do we accept flaky network hardware?
Checksums were added to TCP/IP because of bit rot in the early IMPs and we've kind of accepted that network hardware is going to be dodgy ever since. Note that the IP header checksum isn't to protect against transmission errors (that are detected by the link layer checksum), but against errors occurring after an error-free reception.
Yet we don't extend the same leeway to storage hardware, for example: write a block of data from memory onto a disk and there's no checksum to protect against bus errors in the transfer. If there was over time an accumulating corruption of our data, I think we'd have noticed, so I can only assume these devices simply work better.
So the question, really, is how are these network card vendors getting away with it?