What is the purpose of the 10th Amendment?

Why this is the answer

The 10th Amendment says that powers not given to the federal government belong to the states or to the people. That is the official answer; the opening words "It states that the" are optional. In its own language, the amendment reserves to the states, or to the people, any power the Constitution neither delegates to the United States nor prohibits to the states. It is the last of the ten amendments known as the Bill of Rights, which were ratified on December 15, 1791. It grew out of a worry that was widespread at the time. The Framers had concentrated on building the structure of government, and many Americans wanted written limits on what that government could do. They feared a strong national government would take away the rights won in the Revolutionary War. James Madison, one of the Framers, drew up a list of individual rights and limits on government, and those became the first ten amendments. The 10th Amendment states outright an idea that runs through the whole Constitution: power is divided between the national government and the state governments, a division called federalism. Under that arrangement the federal government is a limited government. Its powers are the ones the Constitution describes, and most of the rest belongs to the states. That is why states run schools, provide police and fire departments and issue driver's licenses. Watch the last part of the answer. The amendment reserves powers to the states "or to the people," and leaving the people out gives only half of it. Another mistake is mixing it up with the amendments that protect people accused of crimes, such as the right to a jury trial or to a lawyer, which come earlier in the Bill of Rights. An answer saying it gives all power to the federal government has it exactly backward. To remember the number, think of it as the closing piece of the Bill of Rights, the one that marks where federal power ends.