Some people benefit from receiving individual counseling before going through couples counseling. Individual sessions with a therapist allow them to work on specific issues that might hold them back from making progress in couples therapy, such as anxiety.
A person may know for sure that they have personal issues. Thus, it can be beneficial for them to go to therapy on their own for a few sessions before they start going to couples counseling. They might even suggest that their partner sees a therapist on their own as well.
On the other hand, for those who are on the fence and nervous about individual therapy, beginning with couples counseling might be a better choice. A couples counselor can then let them know if they think individual therapy is needed.