Why is it important for Congress to expand or contract the Federal Courts? Why not the President?

Short because the Constitution says so.

Complex The United States Constitution established only one federal court—the United States Supreme Court. Beyond this, Article III of the Constitution left it to the discretion of Congress to “ordain and establish” lower federal courts to conduct the judicial business of the federal government. Congress established a host of different federal tribunals to adjudicate a variety of legal disputes.

i think it's the cabinet

answer; omb;