I quite often asked this question myself but realized that much of the works out there simply are not focused for those fluent in the field. Granted, that doesn't mean someone from the field can't read it; it's more of a factor that the work is meant to appeal to people outside of the field too.
For instance, a document explaining how to use a piece of software, while it will obviously be rudimentary to people who use the software, the "John Does" of the world might not even understand the point or some of the spicy terminology. The software could be something like Microsoft Paint (where the use-case is at least somewhat intuitive) all the way to complex software development software such as NetBeans, Eclipse, and IntelliJ IDEA. Think of it this way: If I wrote a paper on how software is made but I use what are basic terms (such as compiler, IDE, etc.) to me, would you be able to understand what is going on in the work?
I would argue that having such details on some of the concepts may help people such as new learners to the field or even spark the interest of those who were not previously interested in the field. Reading works of others when I was much younger has prompted me to take up the field I've taken now.
I rambled a bit, so I'll summarize. It is because those not as fluent in the field will likely read the work or in the event that someone such as that does, the work can at least assist them to understanding basic concepts and terms used within the work.