Perhaps for programmers the need is not evident, but for anyone who writes long documents, it's indispensable. It's indispensable enough that I am still using Microsoft Word for anything that has any sort of header/subheader structure. OO and LO are OK for short letters and memos, but if it has more than 2 headings it gets clunky because of the lack of outline mode.
The core difference between writing text and writing code, which apparently the programmers working on OO and LO fail to grasp, is that writers are producing text which will be read by humans, not executed by machines.You can't just comment out the cruft and do a GOTO jump over that module you decided you don't want, then tell them to go back 17 pages to pick up the information in paragraph 3. Writing needs structure and flow to lead the reader through the material in a way that make the content comprehensible. It needs primary and subordinate ideas. Order and levels of importance are important. In Microsoft Word, collapsing the document into Outline mode and seeing the heading and subheading structure makes the flow of the document visible, and more important, the means to change that flow is on the same screen. There is no interruption in the work flow.
http://www.gigamonkeys.com/code-reading/ seems to understand it, going the other direction: most real code isn't actually in a form that can be simply read .... in order to grok it I have to essentially rewrite it. I'll start by renaming a few things so they make more sense to me and then I'll move things around to suit my ideas about how to organize code. Pretty soon I'll have gotten deep into the abstractions (or lack thereof) of the code and will start making bigger changes to the structure of the code. Once I've completely rewritten the thing I usually understand it pretty well and can even go back to the original and understand it too.
Which leads me to "Issue 3959", wherein writers asked for this on 2002-04-10 20:39:19 UTC ... it's ranked as "Trivial" now. It has nothing to prevent implementation except the inability of the code maintainers to accept that writers really do know what they need in their tools.
Here's the overview of Bug 3959 ... https://issues.apache.org/ooo/...
OVERSHOOT wrote upstream: Ah, yes. Issue number 3959. Originally filed April 10, 2002. More than twelve years ago. In that time it has remained in the top-voted issue list year-in and year-out. Others come and go, but 3959 keeps on pissing off users. At last look, there are about ten duplicates requests on file.
Every few years some developer wanders by and tells the people following it that nobody needs outline view, or that there are tools available to do it, or whatever. Often, they close the issue. In effect, "I don't use outline mode so obviously it's not important." The mailing list heats up for a while, the developer either mumbles something about maybe the team should look into it and vanishes or else just vanishes, but the issue is either reopened or left open. I've seen at least four of those cycles so far. We're probably due for another one.
At this point, I suspect that 3959 will outlive (Open|Libre|Star)Office for the classic open-source software reason: if it doesn't scratch a developer's itch, it ain't happening. And apparently, developers don't outline, edit, or otherwise structure their writing or much care about the people who do.
As the wisdom of XKCD proves - http://www.xkcd.com/619/