Of course things change. Security protocols get upgraded. New attack vectors are discovered in protocols and need to be fixed. New devices with new capabilities are created and need API integration. That all requires human effort to make happen. All of that has to be worth the cost of maintaining the project.
> CUPS still needs printer-specific drivers to do the actual printing part.
Even if it needs them, the point is that it has them now, probably due in no small part ot the fact that CUPS is used on the Mac.