APA format and writing priorities

So often when I ask students about what their worries about class are, many of them will answer something about APA format.  It seems like there's a culture of anxiety about document formatting (MLA usually) that is cultivated in high school English classes.  Or, perhaps high school (or earlier) English teachers are placing undue emphasis on the importance of document formatting in college writing courses.

Is this true?  Why is this?  How much time and/or emphasis was given to MLA or APA format in your high school English careers?  Did your teachers convince you that it really mattered?

Before you write about either of those things, I'd like to share two things:

1.  I was an English major for eight years, basically -- four as an undergrad and four as a grad student.  For all of my English classes I had to use MLA format when I needed to write a research essay.  Without verifying via my transcripts, I probably took close to thirty (maybe more) English classes.  Plus, I also took Honors courses and religion and philosophy courses for which I had to use MLA, too. 

It would not be an exaggeration to say that over those eight years I may have written 100 essays or more that required MLA format.

I was last a university student in 2003.  Since then, I have taught college courses, mostly writing ones, for the past sixteen years.

I have not used MLA format once since I used it as a college student.

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2.  At the University of North Dakota I once taught a capstone course to seniors whose majors did not offer a capstone of their own.  My course was a kind of any-majors capstone (doesn't really make sense) that was intended to give students a kind of capstone experience.

The course focused on the goals and successes and failures of modern universities, with special emphasis on how universities and their athletic departments coexisted.  The course was reading, discussion, and writing-intensive.

I learned very early in the semester that nearly all of my students had not had to write an essay since they had taken Composition II.  So, that means that most of them went five semesters (at least), or roughly twenty-five classes, without having to write a single essay.

I was flummoxed.  This was so alien to me and my college experience.  It is, however, not that far from the norm, I suspect, for students who aren't humanities majors.

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This brings me back to my questions above.  Why is there so much emphasis placed on learning a document format (MLA or APA) in high school English classes when that skill is almost totally irrelevant after college and nearly so in college?

MLA and APA format (any document format) are completely irrelevant to the writing process.  There is no way to write in MLA or APA; they are formats you impose on essays after they are written. 

Document formats don't matter when you're generating ideas, posing research questions, finding credible sources, reading those sources and taking notes, writing an outline, creating a rough draft, revising a rough draft, or proofreading for grammar, mechanics, word usage, etc. 

Document format is not writing.

Document formats matter when the essay is finished and you ask yourself, "Does this look like it's supposed to?"

What are the real purposes of teaching document format?