I always found it curious in my classes, there would be this single way to interpret something written in a novel. There were preset strategies or ways to interpret the theme, characters, behavior, etc. rather than being allowed the chance to think of unique applications of a theory or theoretical framework. How the theory worked internally made no difference; as long as i could make a plausible case that one thing has a link or connection to something else not seemingly related, without compromising the theory, I did fairly well.
Honestly, I think they do this so they can get through it quicker, so they show objectively how much the kids are learning.
If you just let the students pick their own way to interpret things, it would take too long for them to form a view which as sophisticated as what they give you, so they just tell you what to write and judge you based on that so they can more easily report their results, "Look how complex novels we got this year! And you can see from our results that they understand the material". Creativity makes it harder to do an "objective" assessment.
Personally, I think school allows for more creativity in the sciences, because you can actually
show that your working is correct, if it logically leads to the correct answer. Not having a single
what, as per subjects like English, means they have to be more restricting in
how you can get there. To me, mathematics is the subject which allows for most freedom of thought, because it is the subject with the most objective answers. If someone doesn't understand my philosophical ideas, they can't see whether or not what I'm saying is even coherent, but not understanding my mathematical ideas doesn't matter because they can see that I
got to the right answer and so I can do it however I want.
School needs to get rid of objective assessment, and instead focus on helping students reach their full potential.