Why is the Supreme Court so deeply divided on so many questions?

They are divided partly because the American people are divided, and partly because there are different interpretations of the law. It's almost the same reason that you can walk into any classroom or workplace in the country and ask questions that people will disagree on. For instance, in cases where a woman wants to terminate her pregnancy, are the woman's rights or the unborn child's rights more important? Or, when someone who has entered the country without a visa or greencard needs emergency services, what actions should the caregiver take? ... There are thousands of questions to which there is no clear answer in the law. Courts decide different ways... and the Supreme Court has to have the final answers, but those judges are people too, and often during their careers, they have decided different ways on similar questions. Whenever there are questions about which normal people can be deeply divided, then the highest court will have deep divisions as well. They are people, with political and moral leanings of their own. We trust them to be wise and to follow the law, but there is no black and white instruction that they can follow where they will all agree. If it were that simple, they wouldn't even listen to the case. They are there to decide the hardest ones.