Printer drivers are userspace things, they don't exist in the kernel, and they're also not part of the X stack. The kernel, xorg and desktop developers have an interest in making sure video drivers work and install easily because without them, well, you can't see much. Printers are relatively rare peripherals compared to video cards. Everyone has a video adapter, not everyone has a printer.
Plus there's a much wider diversity of printers than there are video cards. People tend to keep printers for longer than they keep video cards, because printers are often useful beyond the few years that a video card is "current" for.
The other factor is the wide diversity of hardware vendors. For video cards there's really only three main players, Intel, nVidia and AMD/ATI, with a lot of smaller companies like VIA and neomagic. There's a gazillion printer manufacturers out there, and each one has a bazillion printers to make drivers for (although most are very similar). Net result is that each printer vendor has their own license terms, driver installation method and relationship with the open source community.
Some vendors 'get it', others don't. I'd recommend contacting the vendor of your printer and letting them know that "ease of driver install" is one of the factors you use when making a decision about which printer to buy in the future.