Business companies

Many organizations create security-breach information repositories (clearinghouses) to collect information about breaches and breach attempts. Then they correlate the information and try to detect patterns or definitive information, which will allow them to better protect themselves, mitigate risk, and alert internal security teams, or even similar companies, to these attacks.

Also, these repositories are prime targets for attackers, so managing them on the Dark Web provides protection from detection and exfiltration of the information and their source IPs.

Organizations that are employee-focused use the Dark Web as a place in which employees can report to management on irresponsible or illegal activity performed inside the organization, without fear of repercussion.

Many companies also have analysts who monitor various websites for information that can help them. Naturally, they don't want their competitors to detect what they're watching (to prevent industrial espionage...