it's not unlike car transmissions.
Today there are plenty of options from excellent torque converter automatics, to dual clutch automated manuals, to single clutch automated manuals, to multi clutch plate autos. They are all excellent and do the job really really well and often are faster changing than any human could dream of. However, driving a manual transmission and getting it right, honing your skill is still an immense pleasure to many. Zeiss provides the user with the pleasure of something mechanical that's incredibly well engineered, designed, and built and the opportunity for the user to get it right himself.
You propose Zeiss could clean up the high end market. They already do. They don't have much competition. It's a small market. Zeiss already sells every lens they make. Sometimes it's not all about profit, sometimes it's about making more than enough, closing the doors for the day, go out and enjoy life.