Supreme Court justices serve for life. Why?

Why this is the answer

Justices serve for life so they can be independent of politics. The official list words it two ways: to be independent (of politics), or to limit outside (political) influence. Either one is correct, and the words in parentheses can be dropped. The Founders did not want federal judges deciding cases with an eye on the next election. They wanted rulings based on the Constitution and the rule of law, so they kept judges off the ballot and let them serve with no fixed term. A judge who never has to campaign or win reappointment has no reason to favor whoever holds power. Alexander Hamilton described the danger in Federalist No. 78. Judges holding temporary commissions, he wrote, could not be expected to show the steady loyalty to the Constitution and to individual rights that courts require. If the President or Congress controlled their reappointment, judges would be tempted to please that branch; if the people did, they would be tempted to chase popularity. Permanent tenure removed both temptations. He also explained why the courts in particular needed that protection. The executive holds the sword and the legislature holds the purse, but the judiciary has neither, and in his words it has "neither FORCE nor WILL, but merely judgment." He considered it the weakest of the three branches, and he argued that nothing would do more for its firmness and independence than permanency in office. The Constitution adds one more safeguard in Article III, Section 1: a judge's pay cannot be cut while the judge remains in office. Wrong answers misread the reason. Justices are not elected by the people, so any answer built on voters choosing them is wrong. Lifetime service also has nothing to do with saving the cost of elections. To recall the official answer, think about what a Supreme Court justice never has to do again after confirmation: run for office, or ask anyone for the job.