Courts should be open for people to see what is going on. The Supreme Court should have nothing to hide and cameras don't talk back or disturb so there should not be any issue with them. Being able to see what goes on in the highest court would be a treat for many people.
The Supreme Court is the nation's highest legal authority, and since legal authority flows from the people to the state itself, those people have the right to know what happens in their government, and this certainly includes the Supreme Court. The population has a right to know that cases are prosecuted effectively and justly, and that the decisions reflect the constitution and the best interests of the citizens of this nation as a whole.