Why are presidents elected?

Most other positions of leadership: military, judicial, corporate, etc, are all promoted or appointed.
What sets the president apart from those leadership roles? Why should we not "elect" our military commanders? Is it that the head of armed forces needs specific skills honed through years of experience while the head of a government ... can be Joe Blow?

This just ran through my head, and I figured it'd spark an interesting discussion.

Jam it back in, in the dark.

Originally Posted by Lord Styphon

If Joe Blow is a natural born citizen, at least 35 years old and has been a resident in the United States for 14 years, Joe Blow can be president.

What kind of things does a president do? Is there any kind of specialized training necessary to perform those duties?

Because if there are duties, then those who put him to do that job ought to be aware and knowledgeable of those duties so that they can place the best possible candidate.

I'm trying to say, the average person doesn't know the president's job, and hence can't choose a proper candidate for the job. And since it's such an important position, it shouldn't be left around willy-nilly like that.

There's nowhere I can't reach.