What workplace would have an issue if you had an anatomy textbook on your desk, for example?

All kinds of places. Imagine being hired to do a certain job, and you have a completely unrelated book of human organs open on your desk or your screen? Imagine if your job is public-facing. There are plenty of scenarios in which that's either weird or risky, and if you can't grasp that concept, I don't know what to tell you.

You see this as being vulgar

No, you're completely missing the point when you come up with nonsense like that. Indeed, before my disability set in, I wanted to be a heart surgeon as a kid, and would leaf through my dad's anatomy texts in fascination and build models of various human organs. Point is-- this is in no way about my personal tastes. That's all in your own head.

Again, and this will be the last time I try to draw such a map for you, the whole point of the NSFW label is to communicate to people in all possible workplaces that certain content might be risky to view in said workplace. That's all.

This isn't about certain scenarios you might imagine to yourself in which it would be absurd for anyone to be concerned about such things. There are certainly plenty of those! This isn't about censorship issues, which you seem to repeatedly confuse the issue for. This is about a friendly, harmless warning tag that lets people know when there MIGHT be a risk for their workplace. Now what people do with that is certainly their business. For example, in settings you can choose how you want such things to display. Either blurring them, omitting them, or taking no action whatsoever. Bam. Problem solved.

Now if you're just out to waste my time and have no real interest in understanding, then congratulations. Mission accomplished, I guess. Bye.