While I was visiting Venezuela, I observed that most of the printers that you find in a governmental office were HP (at least on those offices that I visited). A person, that is a subject in my thesis so I cannot talk about him/her, explained to me why HP was dominant. I won’t go further in his/her explanation (you would have to read my thesis), but you could check the page of the Linux Foundation. Specifically that is the page that describe how Linux-friendly are the printers by brand. Then, you will understand.
The government is one of the biggest buyers of office supplies in any country (that includes printers and ink). If I were a printer company, I would try to approach the FLOSS community.