It makes them more independent. If they had a limitless amount of terms, they could just vote for whatever was suitable at that time and keep their political power. Since they won't be able to stay in the congress longer, then they can vote whatever they want because there's nothing that will affect whether or not they get elected again.
In 1898, the Spanish-American War broke out, and the strategic use of the naval base at Pearl Harbor during the war convinced Congress to approve formal annexation. Two years later, Hawaii was organized into a formal U.S. territory and in 1959 entered the United States as the 50th state. Without that advantage we would have lost
