It sounds cool when you do it right, that's why.
Ok, the question, as I understand it, involves how it's written out. Why is it written to resemble grace notes instead of being written out? Your answer to the actual question seems to be:
"The reason that it's written like a grace note rather than writing out the notes, is because it sounds cool as f u c k. If the notes were not written out, then it would no longer sound cool as f u c k." More likely you didn't understand the question, and though someone was asking why are there appoggiaturas.
Fact is that some of us are interested in these things. If you aren't, then don't get involved in topics that bore you, but why get mad because others are interested?
I actually think it is an important question,
because this notation gets misplayed. People see it as a grace note and play it as such. In this particular piece it's rather obvious, but there is a piece played as a beginner or early intermediate piece where half the students and teachers put in the wrong note values and to my ear it distorts the piece. So
we have to know about this in order to not misinterpret music from a certain period where this was the norm.
My teacher once told me the reason, and I think it was the one already cited --- to prevent people from adding ornaments to this kind of appoggiatura, which the musicians of that era were doing in those composers' lifetime. For me as a student it was important to know that, or I would have played the music wrong too.
Topic: What is the use of appoggiaturas...