Interesting... just a shot in the dark, but perhaps it's because they are a .ca registrar accredited by CIRA and as such had a Canadian business presence (office?) and were eventually required to start collecting sales tax from Canadians?
Microsoft also collects HST & PST for their online products (domains, hosting, Office 365, etc)...
Death, taxes and no renewal codes when your domains are set to expire... 3 certainties in life.