[bsilvereagle]

I believe this is because the tracking dots[1] require yellow ink.

[1] https://w2.eff.org/Privacy/printers/index.php

[kuschku]

Well, why can I print with just black ink on my canon and HP multifunction printers then?

(they also allow me to do high-res (4800dpi) scans of money without any issue, in hilarious contrast to photoshop, which refuses to open them)