I agree with Sean, in that I have always said we could bifurcate courses, not equipment, if only owners would realize that catering to the top <1% who want to play over 7K isn't necessary for most courses. I don't know how it would happen. Would state or local golf associations step in to help determine which "championship" courses would be downsized? I believe many residential courses would be heroes by giving up back tees for gardens, dog parks, or tot lots.
However, there are those who still push the "We need 7K" narrative, despite some recent data that shows 91% of men prefer to play 6300 yards, or less.
In those cases, if form follows function, 6 or 7 tee markers (perhaps some combined as in the example of senior men not wanting to play from the red markers, but may play 5 yards back with their own white markers) makes some sense. Looking at drive distance data, they pretty well congregate around 6 distances (7 if you count juniors that hit it 100 yards or so, max)
If the goal is (and what business owner wouldn't want this?) to make the greatest number of players happy, providing a course with optional lengths at their comfort level makes sense. Obviously, tees in almost all senses are typically under thought out, particularly forward tees, but that is changing. Some architects do better - Fazio would split forward tees wider outside the line of sight from the back tees and hide them with gentle grading. Art Hills always put a small roll at the back of mid and forward tees to try to hide them as well. Better and more design thought is generally needed.
However, in the scheme of things, basically, course owners and architects will ask longer tee players to put up with some bad views as the price of sharing the course with the lesser talented. In golf, and maybe US society, the idea of sacrificing something not essential to you for the common good seems to be in decline.
Lastly, yes, it can cause more walking to tees, but does it increase walking overall? And, as tees expanded, in new routings, I always tried to make the most used tees the shortest walk from the previous green. And, shorter tees also cause 8-10 fewer "unnecessary" shots by average players, so it probably all averages out, time-wise. I agree that it probably leads to more cart use, but that boat has sailed at most places anyway.
I am not the biggest fan of most combo tees, as they usually take the short tee on the longer holes and long tee on shorter holes, so every hole plays a similar yardage in most cases, and the advantage of reachable greens is offset somewhat by using similar clubs each time.
I also agree with Joe that obviously, topography supersedes pure math in tee design, much like fw bunker placement. It is not necessary for EVERY tee on every hole to be a perfect percentage of the back tee length.