My great grandfather emigrated as a young person and started using his father's patronym as his own last name instead of continuing to use his father's first na

My great grandfather emigrated as a young person and started using his father's patronym as his own last name instead of continuing to use his father's first name as his patronym. He could have kept the patronym tradition alive, but why? He was in America now, and once his kids were born, they mostly spoke English anyway.