In the United States, all "Inferior officers" must be confirmed by the Senate, unless the confiring authority is delegated as per Article 2 Section 2 Clause 2 of the constitution:
and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein other- wise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments.
In addition, all Civil Officers of the United States are subject to impeachment as stated in Article II Section 4 of the U.S. Constituion:
The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.
However, no where is it mentioned in the constitution can congress delegate the ability of impeaching executive officers to anyone else. That is, unlike confirmation, impeaching inferior officers of the executive branch can only be done in the way outlined in the first part of Article I, Section 3 Clause 6 (emphasis mine):
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.
The ability to delegate one but not the other seems like an inconsistency to me. Hence I wanted to know...
Why is the Senate able to delegate it's confirmation authority for inferior officers of the President, but not delegate it's impeachment authority for inferior officers likewise?