The main function of (nearly all) academic writing is to help readers better understand something they want to understand well.
Consider a simple before/after account of an academic text. For the text to serve its function, readers need to feel that they understand something better after they’ve read the text. This means that at some point in the process readers need to feel that there must have been something inadequate in their understanding before they read the text. To perceive that the ‘after’ situation is better, they must perceive that the ‘before’ situation was worse. Sometimes this is not difficult: sometimes, readers know that their understanding is inadequate on just the point that a text will address. But often, readers do not know. It is often the case that the text itself must show readers the inadequacy in their understanding.
This function of showing the inadequacy is what we’ll call constructing the problem. Again: your academic text must serve the function of making your readers’ understanding better. To do this, your text itself will probably need to show readers that their understanding is inadequate. You do this by constructing a problem: at the beginning of your text (and likely, at other points throughout the text), you articulate the readers’ problem in understanding something that they want to understand.
But nearly all academic writing—to serve its function and have any value—must be responding to a problem of understanding. The function and value of an academic text is that it is the solution to its readers’ problem of understanding.
Note that “solution” does not mean: “complete, final, definite solution”. Many academic problems have no such solution. ‘Solution’ in this setting need not have the same sense as the solution to an arithmetic problem. Solution here means only that your work helps readers understand something better, even if the progress is tentative and incomplete
Unfortunately, many conventional models of introductions fail to show value. US schools for many years relied on a model of writing in which the function of introductions was not to establish value. This isn’t surprising: as we’ve seen, students do not, in fact, need to use their writing to establish its value for their teacher/readers. The value is established in another way: the teachers are paid to read.