Why can’t they? Sure, they can’t just call up the FBI or other US law enforcement agencies and refer the matter.

However, they can absolutely use the threat of disclosure of sensitive information to blackmail or otherwise coerce someone. The threat (real or perceived) many times is worse than the reality.

I’d say they each have the capability to cause harm, but the incentives/motivations/safeguards that might drive (or inhibit) them to do so are drastically different.