I had the interesting experience of maintaining a device driver written by a hardware engineer, for a servo motor. There was no reason for it to be in assembly language, but it was. No comments, either. Very bright guy, but he'd just never absorbed much common sense about coding up maintainable software.

I think the thing here is that, for the most part, hardware guys don't want to write software, so they don't bother to learn how to do it right. This usually comes back to bite them in the ass, when they end up needing to write some code anyway.