I disagree. They are not tasked with keeping us safe; they are tasked with safeguarding our liberties.
I guess you aren't a big believer in the US Constitution then. There seem to be things like the army, navy, militia, and common defense mentioned. I also see that the President is given the power to grant Pardons. Might some people be in jail for breach of peace, reducing the "safety" of others? You might think so.
Preamble to the United States Constitution
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
Clause 1: Command of military; Opinions of cabinet secretaries; Pardons
The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States; he may require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any Subject relating to the Duties of their respective Offices, and he shall have Power to grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment.
Your oversight is understandable. People here are all about Amendments 1, 2, 4, and 5. They don't really care much about any other part of the Constitution, and that inattention shows.