Final answer:
The Supreme Court justices serve for life with good behavior to protect them from political influence and allow them to make impartial decisions based on the law.
Step-by-step explanation:
The former reasoning for having the Supreme Court justices serve for life with good behavior was primarily because they did not want the justices to be subject to the whims of politics, the public, and politicians. This was to ensure that the justices could make impartial decisions based on the law, rather than being influenced by popular opinion or political pressure. By having lifetime tenure, the justices are able to interpret the Constitution without fear of losing their position or being swayed by temporary political interests.