Are you old enough to remember Winmodems and NDISWrapper? There used to be some hardware that was so cheap that the Windows driver needed to do some of the basic work. They were never compatible with anything but Windows (and maybe 98 or XP at that). I’m sure there were some printers like that.

Combined with poor driver support early on, and a lack of standards (at least on the consumer end), and the need to have a separate PPD file for every make and model of printer, and printing used to be a mess. (It almost got bad again when Microsoft tried pushing their XPS format as a replacement for PostScript, PCL, PDF, and EPS, but that didn’t catch on.)

Apple buying CUPS (and hiring its lead developer) was great for the community. They got it working all but perfectly. I’ve never had a problem printing on Linux; HP, Brother, or otherwise.

FYI: the developer quit Apple and forked his project into OpenCUPS, but I haven’t tried that.