A dust particle, for example, looks like a boulder as it approaches the head of the disk drive. To help eliminate this problem diskettes contain a liner that is supposed to catch these contaminates and keep them from damaging the disk. It is impossible, however, to completely remove the possibility. If media is poorly manufactured it may contain a substantial amount of debris that might be caught by the liner during duplication, then later become dislodged and eventually scratch the disk. Or, a customers drive might reside in a dirty environment or receive infrequent use and subsequently have dust build-up on the drive heads.
Diskettes contain a substantial amount of data written in a very small area.
All of this requires precision in both the write cycle and the read cycle. Software manufacturers can control the write cycle, but the read cycle is beyond the control of everyone except the end user. Diskettes are extremely sensitive to magnetic fields. Most shipping companies are cognizant of this and try to avoid exposing electronic media to harmful devices. However, mistakes do happen.