With respect to the question of whether and how the right to privacy is protected by the United States Constitution, why were there so many individual cases on the issue heard by the Supreme Court?
Between 1923 and 2003, there were eight cases pertaining to the U.S. Constitution and the presumed right to privacy decided by the United States Supreme Court. The reason for so many cases is implicit in the span of time over which they are listed. Even clearly enunciated constitutional rights, for example, freedom of expression, are open to interpretation (no yelling "fire" in a crowded theater, for instance). In the case of the issue of privacy, the matter is considerably more vague.
There first ten amendments to the Constitution comprise the Bill of Rights. Of those ten amendments, four (Amendments I, III, IV, and IX) are applicable to the issue of privacy. Plus, the Fourteenth Amendment includes the clause denying any state the right to deprive any citizen of "life, liberty, or property, without due process of law." Because none of these amendment specifically uses the phrase "right to privacy," the question of whether such a right exists and, if so, what are its limitations, is left for others to decide. In the United States, that means the Supreme Court.
Throughout the 20th Century, legal cases involving the right to privacy (often invoked in cases of questionable search and seizure operations conducted by law enforcement agencies) have emerged that defied easy resolution. Because the issue is fundamental to Americans' sense of freedom, the Supreme Court occasionally decides to study the case and make a determination as to whether an individual's "right to privacy" has been invaded.
The decision issued by the court in one of the "right to privacy" cases decided by the Supreme Court, Griswold v. Connecticut (June 7, 1965), includes language that goes to the heart of the matter:
"The foregoing cases suggest that specific guarantees in the Bill of Rights have penumbras, formed by emanations from those guarantees that help give them life and substance. Various guarantees create zones of privacy...We [the Court] have had many controversies over these penumbral rights of "privacy and repose." These cases bear witness that the right of privacy which presses for recognition here is a legitimate one."
In John Geddes Lawrence and Tyron Garner, Petitioners v. Texas (June 26, 2003), Justice Kennedy wrote in the deciding opinion,
"Liberty protects the person from unwarranted government intrusions into a dwelling or other private places. In our tradition, the State is not omnipresent in the home."
Each case heard before the court regarding privacy represented a slightly different legal distinction requiring action by the highest court in the land. That cases involving the "right to privacy" continue to reach the court system is testament to the difficulty of drawing parameters around basic rights such as are covered by the Constitution. As the technological means of gathering and conveying information continue to evolve, these issues will only become more difficult to judge.
Without knowing which cases you are referring to, it is impossible to answer this question in any specific way. Therefore, we can only answer this in a very general way.
Generally, cases need to be decided by the Supreme Court because they present issues of law that are both very important and very difficult. The Supreme Court gets to decide which cases it will hear. It only hears those cases that involve cases of law that they believe to be important. For example, the Supreme Court is going to be deciding a case about affirmative action in this session. It feels that this is an important issue of law and an important issue for the country. The Constitution says that all people shall enjoy “the equal protection of the laws.” The Supreme Court needs to decide whether this means that colleges and universities are prohibited from taking race into account when they make decisions on whom to admit. This is the sort of issue that is a very difficult thing to interpret and it is an issue that has major implications for the country as a whole.
Thus, the Supreme Court takes those cases that present important and difficult issues of law.