I hate to oversimplify matters, but I've never received a good answer to this question:
CDs are just made up of pits that represent data. So why can't we have a copier (and software) that will copy it bit-by-bit, without caring about sectors, tracks, TOC, etc. Just SEE A PIT, WRITE A PIT! What's holding back this TRUE raw reading and writing? Hardware or software? Even the software that claims to use "raw" modes are caught up in sectors, tracks, settings, etc. Even with weak sectors, this shouldn't be a problem. And the so-called "unreadable" parts are not really unreadable, they're UNINTERPRETABLE. If it were truly "unreadable," a writer could just burn garbledy-gook in the same place and no CD-ROM could know the difference. We even have software tools that can compare how closely a CD has been copied, yet we can't use the same technology to copy it better? Why doesn't it forget formatting, interpreting, and settings and JUST WRITE EXACTLY WHAT IT SEES?
Like I said, maybe I'm making it too simple.