This and exactly this; 2D printing technology is sealed tight because of those damn microdots. Lulz

I wonder if this is why color printers won't print out black & white print jobs when they run out of color ink, even if they still have black ink.

Yes. But this is unrelated to the question they asked.

I don't think so. The current situation suggests that we really need an open-source printer, because otherwise there is no privacy at all.

The question wasn’t whether there was a need. The question was why there isn’t one. That agreement doesn’t prevent you or anyone else from making your own design.

A common answer to "the question" is that passably good printers are dirt cheap, and excellent printers are highly complex multidisciplinary efforts. Things don't exist in the open source world unless somebody has a need, or passion, to make it happen.

Given the availability and complexity, the question becomes "why bother." Microdots are an answer to that.

Then I'd ask, is there a legitimate purpose? Supposing the end goal is a totally open source chip foundry: yeah, you don't want microdots on your masks. Edit: oh god, and printers that won't do b&w without yellow dye available.

[citation needed]

My printer is out of yellow ink but it won’t let me print in Black and White mode.