D6's are the norm in my area for size, when the high drives came out, most old timers then refused to run them, the complaint list was so long, if anyone actually wrote them all down, it would be a very large book to say the least. Mainly those young enough to change got used to them and after the old timers all faded into memory, the sales picked up and since CAT offered nothing else, you could say take it or leave it sort of philosophy, you could say sales of high drives rose steadily?? verses what, selling nothing at all??
I've ran both high drives and oval's, never saw firsthand all the benefits CAT has shoveled all these years, even after telling me how much better they are so many times I could retire several times over if they'd have paid me a dollar for every reminder of the benefits.
If your running the machines daily, year in and year out, thousands of hours per year, those benefits might work out, for me who own and run many machines with few hours per year on each in the overall scene of things, I'd do a transmission and finals maybe once per machine in my lifetime, the disadvantages outweigh the benefits ten to one.
As for other makers building high drives, first off the patents ran off years ago, as in decades ago by now, and yet only a handful of prototypes have been put out and not many went beyond that point, which speaks volumes to many us.
Next is, if all these benefits are note worthy, why isn't every machine Cat makes, high drives including hydstat's in the smaller dozers, don't those machines have finals and motors as well that deserve to up out of the mud, muck and filth?? Wouldn't changing finals on those machines much better if they were up top verses down in the crud as well?? Or in the bigger picture wouldn't they be able to compete in the price of dozers and lose sales??
But above all else, lets not forget the famous, bragged about, trend setting, setting new horizon's, leader of technology to set the norm for centuries to come, of the great, slow speed high torque diesel engines on dozers?? Which also never went over industry wide, only to flop and fizzle out and now ever CAT's people say to not buy a dozer with those in, the repair costs are too high and parts are getting scarce, etc, etc, etc and not one other makers ever got on board to mass produce those style of engines or dozers with them in, but at the time, it was all the rage and a CAT exclusive..............much like high drives.................question is, will they do a better job of keeping the high drives alive over the old slow speed, high torque engines of years ago. But then again if I recall, after all the bragging is done, CAT is no longer in the over the road engine market either, leaving all those die hard truckers to wonder what happened to the best maker to ever build engines only to refuse to sell them to those same folks who spend their entire life bragging about them, to buy and run something else and where is all the bragging now of the industry leader?? those trucks run just fine with cummins, detroit and now many others doing the leading.
But I guess when you quit making engines for the over the road market, that's the time to build a truck, powered with an engine that can meet emissions and bought from a competing company of CAT to power that truck.........but I know, I should just shut up and leave it alone, after all, CAT is the leader of the industry, and also the first the get out of those same self trend setting trends, did I hear and see CAT now makes an electric oval track machine?? where's the high drive on that, electric motor in the mud, much and filth, now that makes perfect sense..........to CAT, doesn't that machine have finals or do the tracks fasten directly to the motors, where are those bragging about all the track benefits of the high drives for the electric dozers?? But above all else, do the electric's start better in frigid weather than those famous slow speed high torque Cat exclusive engines of years gone by. And to think I can't order a brand new high torque low speed diesel in a new D6T, such a bummer, after all I was told of the benefits of those engines over the years, couple that to a high drive and I'd have thought, it would be an ideal dozer, the best of all worlds, both high torque low speed engine and high drive.
But to answer your question, I think it gets down to a company trying to sell machines with their designs built into it and its up the customer to decide if those benefits are worth it or not is about the jest of it.