Here's what I think is happening. The moderators on SO have decided that there are certain classes of questions that are unacceptable and should be closed. I agree, so far.
Now, that question is of that class, so it has been closed. However, there are exceptions. Normal humans are good at making exceptions and should have made one here. A certain type of personality -- one that's over-represented in engineers -- likes to create systems that don't have exceptions. They like to create abstractions. And then you get this.
It's also why you have people who still organize their email, even though search obviates that problem.
FWIW, it's not the moderators who've made these decisions...
Like it or not, the types of questions you see allowed or discouraged on SO are in large part the result of years of discussion, debate, and collaborative moderation by a rather large portion of the userbase on SO. Even the handful of people able to take unilateral action to include or exclude questions are elected - hence the event that instigated this thread to begin with.
Ultimately, the folks with the most power over these decisions are the ones using the site. If you don't like what's being closed, cast your re-open votes and convince others to do likewise.
That particular question ended up being closed and reopened multiple times, and discussed heavily on meta. Ultimately, it reached the point where it was simply unmaintainable, in spite of the hard work of many people involved. So it was locked to preserve it.
If you visit some of the more well-maintained tag wikis, you'll notice they contain sections for freely-available books amid links to other useful learning resources. This tends to keep them smaller, easier to maintain, and much more likely to be maintained by folks who know something about the topic. Example:
Now, that question is of that class, so it has been closed. However, there are exceptions. Normal humans are good at making exceptions and should have made one here. A certain type of personality -- one that's over-represented in engineers -- likes to create systems that don't have exceptions. They like to create abstractions. And then you get this.
It's also why you have people who still organize their email, even though search obviates that problem.