Confidentiality is a virtue which states that you need to secure information by limiting computer access to authorized personnel only.
Keeping confidential data is crucial especially if your business deals with very important information about a person and his security.
Trust is built between a company and a client. The client trusts the company to keep his information secure and confidential from outside parties. Once the confidentiality of the company is compromised, the business will suffer because clients will no longer trust the company to keep their data secure.