Because depending on what level the software is operating at, it may not even be aware of the correct data, and the file format used to store the image might no

Because depending on what level the software is operating at, it may not even be aware of the correct data, and the file format used to store the image might not be capable of representing it accurately. I'm simplifying here somewhat for space, but the CD-ROM specifications allow for at least two ways of storing the data on the disc. A 100% vanilla data CD-ROM with no copy protection uses 2048 bytes per sector for the data that's visible to you as a user, and the remaining 304 bytes in that sector are used for data that helps recover the user-level data if any of it is unreadable (kind of like a RAID5 setup).[1] Mode 2/XA discs (or mode 2/XA sections on mixed-mode discs) use those 304 bytes per sector to store user-level data instead. i.e. they are trading more space for less reliability. PlayStation games are the most common example. If you've ever tried to copy XA audio or STR video files off of a PlayStation disc in Windows and wondered why you got an error, or why the files copied but were corrupted, that's why. Your PC was only copying 2048 out of every 2352 bytes in each sector. The ISO file format for discs can ONLY support 2048 bytes per sector. This is why groups like Redump use bin/cue for anything that comes off of a CD. If you convert a bin/cue to ISO, you are throwing away a little over 10% of the data in every sector. If you want to learn more about this, read the specs for different types of CDs and CD-ROMs. It's a big mess, and I think everyone is happier that the industry standardized down to fewer options in the DVD era. [1] This is in addition to the physical-level redundant data encoded in the pits on the disc itself, but AFAIK almost nothing can read discs at that level.