All types of writing require context.
That's why we write titles, headlines, abstracts, introductions and summaries.
Unfortunately, few writers are experienced enough to recognize that context goes beyond a mere lead-in to the meat of the text.
Providing a good context actually involves filling in all possible blanks in the reader's mind.
Is this something I want to read? Why would anyone take this kind of position? What's the motivation behind the piece? Is this a good fit for my aptitude level? These are all things the reader will ask and that you'll have to answer if you want to provide the complete context for your writing.
More than setting up the material, context lets readers know whether the piece is something that's interesting to them.
Should it matter to them because it's entertaining? Is it of value to their professional knowledge? Will it help them improve in any way? Essentially, it's a way of letting the reader dive into the material with no lingering questions, assured that it's in their best interest to read through it.
Providing context is usually accomplished best after the initial draft, right around the time you're considering whipping out the grammar software and tools.
By that time, you'll have a more or less concrete idea of who will benefit from the piece and what information they will need to be convinced of it.
Whether you're writing an email or a book, the dynamics remain.
Proper context needs to be established to make the whole experience more useful to your readers.