Various parties entrust you with important information. Conversely, your company or organization provides these parties with important information. That information is contained in many different documents and data. You want to organize access to this information properly, for both your own employees and external parties.
You might want to provide varying levels of access depending on the situation as well, e.g. complete access from within your internal network, but only limited access from external locations. The information may need to be encrypted. In any case, you want to prevent the information from getting into the wrong hands.
New, increasingly strict legislation such as the new General Data Protection Regulation (GDPR) provides some guidelines here as well. You also want to guarantee the authenticity of the data and documents themselves.