Permanence : To provide current information, including where objects (or information about them) can be found on the Internet. Information about a digital object may change over time, including where to find it, but its DOI will not change. When properly maintained, DOIs help solve the problems of dead links and link rot.
Aid citation tracking and sharing or data management and data sharing : To promote and monitor re-use, enable compliance with funder requirements
Required : DOIs are required for some citation style guidelines, such as APA.