Supreme Court justices serve for life. Why?

What does this answer mean?

Supreme Court justices serve for life to be independent of politics. USCIS also accepts "to limit outside (political) influence."

Justices don't run for election and don't need to be reappointed, so they don't have to please voters, a president, or members of Congress to keep their jobs. That lets them decide cases based on the law and the Constitution, even when a decision is unpopular.

Alexander Hamilton made this argument in Federalist No. 78. He wrote that judges should hold office during good behavior, and that judges who depended on someone else for reappointment could be swayed by that person. The Constitution backs this up in two ways: judges serve during good behavior, and their pay can't be reduced while they're in office.

Independence matters because the courts sometimes rule against the other branches, for example by deciding that a law goes against the Constitution.

At the interview, say "to be independent of politics."