I am not sure if this ever worked as "planned," but since the role of justices in today's world seems to have shifted from interpreters of the Constitution to makers of the law (although this has always been part of their role), they have become much more politicized than they had been in the past (perhaps ... there's a lot of controversary about this too). Because they are appointed for life (and therefore not subject to the vagaries of the electorate), there is no way to evaluate their performance on the bench short of impeachment. The role of the Senate is as ms-mcgregor has outlined. And it's an interesting problem. If the President could appoint justices alone, then the two branches would effectively become "executive"; if the Senate alone could do it (if, say, either party had a 61 seat majority), the the court becomes an extension of the legislative branch. I think it's a very interesting problem and one that needs to be addressed. The original intention was for an independent judiciary; I don't know if that can be created under the present system.
The source below might be a place to start investigating the history of the Court.
The Senate must confirm the appointment of all Supreme Court justices. This is to ensure a balance of power between the Executive Branch ( the president) and the Legislative Branch ( Congress) of government. It also offers a system of checks and balances between both branches. The president cannot appoint a member to the Supreme Court without the Senate's approval. In Constitutional Law, this is called the right of Advice and Consent.
Under Article 2, Section 2, Clause 2 of the U.S. Constitution, the Senate's role is to advise and give consent to the President's appointments for Ambassadors, Consuls, public Ministers, Judges of the Supreme Court, and other officers.