Playstk, I am not sure but I think you are confusing Transfer Agent (TA) with registered agent (RA).
They are different persons or entities with entirely different responsibilities.
A transfer agent is responsibile for maintaining the shareholder roles and transer of stock ownership and issuance of certificates.
A registered agent is position mandated by law in all states. Most states require a corporation to have two officers, a president and a secretary who have to be different people. They also require a registered agent who may or may not be an officer of the company.
The sole purpose of the registered agent is to accept legal service of process so that legal proceedings might be easilly begun against a corporation. A lawsuit is deemed served when delivered to the RA even if never forwarded to the corporate officers. Most large and many other corporations hire one of number of firms who exist to serve as registered agents.