Is this about me...or you? Author, audience, and purpose in writing

Recently my students had an assignment to locate a job posting and craft the fitting letter to apply for it, then turn it in for feedback. Once I collected them, I saw one student do something kind of surprising from a rhetorical viewpoint in the opening of the letter, and I thought, “Huh, that is a strange choice,” then I wrote some feedback on it, and moved on.

Then I saw another student make the same choice.
And another.
And another.
I ended up writing feedback on this particular choice numerous times as I graded 48 application letters.
The choice the students were making was to open their letters with a statement that was some variation of “this position would really be perfect for me because…”
Basically, this reads as “this job will work for ME. It’s not about you, and what you need for this position, and how I can fulfill that, but I am applying because it meets MY needs.” That didn't translate to me as a logical reason for why the employer would want to give the person the job.
You may be able to guess that the comment I was repeatedly writing was some variation of, “Remember your audience – you are trying to convince them that you are right for them, not the other way around.”

In short, “it’s not all about you here.”
But this got me to thinking about how well we pay attention to the purpose and the audience when we write. Do they impact our writing in some areas, but not in others? Why is that?
I think we automatically know that something like a cover letter is supposed to be a sort of advertisement of the self, a persuasive piece of writing to try to show the audience you are “right for the job.” Yet, even though the bulk of their letters showed awareness of that, at the sentence level, my students repeatedly lost sight of that. I felt that opening a letter in that way could be enough for the recruiter to get a particular impression of the applicant. (That is, an impression that wouldn’t help them land the job. Muttering "Millennials" and doing an eye roll was my immediate guess of the recruiter's response. Nobody wants that.)
As the writer of any text—and we’re all writers, every day—it’s important to consider what evaluations and expectations you have in your head as the author. In this case, my students were thinking that they wanted a job or scholarship that was particularly fitting for them and their needs. They thought about why it  would be suitable for them – their skills, their goals, their experience, etc. Those are appropriate things for the author to think about before selecting a job or scholarship and applying for it.
However, once it is time to write, a shift must occur to consider the evaluations and expectations that the audience members will have in their heads. Also, what purpose is the writing supposed to achieve? Are you trying to inform or persuade them or entertain them or something else? In this case, the students lost sight—in brief moments in their letters, but in enough moments for it to matter—of the purpose to persuade the audience that they are going to be the perfect person for the job and that their skills or goals will fulfill the audience’s needs, rather than the other way around.
Tweaking the sentence from something like “This job would be perfect for me because…” to something like “I can help achieve the company’s goals for this position because...” would shift the writing from being “me centered” to being more audience and purpose centered.
These choices matter on the sentence-level, whether they are in something as scrutinized as a cover letter or even in emails to clients or colleagues.