https://www.eff.org/pages/list-printers-which-do-or-do-not-display-tracking-dots

(Added 2017) REMINDER: IT APPEARS LIKELY THAT ALL RECENT COMMERCIAL COLOR LASER PRINTERS PRINT SOME KIND OF FORENSIC TRACKING CODES, NOT NECESSARILY USING YELLOW DOTS. THIS IS TRUE WHETHER OR NOT THOSE CODES ARE VISIBLE TO THE EYE AND WHETHER OR NOT THE PRINTER MODELS ARE LISTED HERE. THIS ALSO INCLUDES THE PRINTERS THAT ARE LISTED HERE AS NOT PRODUCING YELLOW DOTS.

I have a theory as to why. CALEA allows the government to compel "a manufacturer of telecommunications transmission or switching equipment" to modify the equipment. Under that or a similar law, printing manufacturers are compelled to put tracking information onto paper.