The problem is a lot of the age machines (Apple II in particular) had a lot of direct control over the disk hardware. So they could move the head in "half track" increments (reading from positions that potentially interfere with standard disk positions) and it is uncertain what on the physical disk is the intended image without somewhat knowing how the drive head is scheduled to move. Obviously something more sophisticated than a drive of the time could image the whole floppy (and one could simulate a drive over that)- but using a drive of the time isn't enough to make usable images in all cases. I think the software that tried to do so were called "nibblers" or "nibble editors", but it has been a long time.