Thankfully, the reliability of computers and their hard drives has improved greatly over the years. They do however, of course, sometimes fail and losing your company's critical information can do damage to your organisation and cost you money.
These days, malicious software such as Crypto Locker can spread like wild fire. If it gets onto one of your computers or servers it can encrypt you critical data in a way that it simply cannot be recovered. It is encrypted with a key, or password, that only the criminals who distributed it know and they will demand a fee, or ransom, for them to release your data. This is a new, and important, reason to ensure you have backups in place; if your data gets encrypted then you can restore it from an earlier point in time rather than be literally held to ransom.