On one hand I disagree because mathematics is abstraction built on top of abstraction many times over. It can be incredibly dense with information. An example comes to mind - Stokes' theorem. It's an amazingly elegant piece of math. It can be stated very neatly with 6 symbols - the integral symbol, omega, d omega, Omega, del Omega and an equal sign. If you were to unravel what each of the symbols meant using the closest terms related to them and then did the same for those terms and you continued some more, you'll have a small book.
This kind of thing is paralled in programming where you rarely want to just push bits around. I imagine you as a person who specializes in assembly complaining about the lack of rigor in more abstract languages.
However I agree with you because the above stuff is sometimes just an excuse for writing terribly. Firstly, there are practical considerations about the sheer length of text. Then you have problems of explaining. A professor writing a textbook can be far detached from that past when they first learned the stuff. My own teachers always told me to never write "obviously" unless I also explain why it is obvious (It can be very useful to explain to the student what needs to be obvious and why).
The best solution I can think of is writing with the online world in mind. A mathematical paper does not need to be short and concise. I envision two versions - the long online version and the shorted published version. There are after all practical and physical considerations in the latter while the former shouldn't be a big deal. In this way whoever is interested in more than the overview can access the longer online version and learn from it.
The biggest problem I see in this scheme is that of laziness - not everyone will want to write long texts.