Like I said before, fanned frets are more difficult to play, but you get a proper low B along with increased clarity and balance for all of the strings. Despite what some traditionalists have said, there is a very discernible audio difference in the low B. Whether you choose to hear it is another thing entirely, but physics don't lie.
I don't think anybody is suggesting that multiscale basses take over completely, just that there ARE people who want the tone that is only achievable with them. These people will put in the extra time and effort necessary to play them in order to add that tool to their toolbox. No reason to shout "solves a problem nobody has!" Some people would have said the same thing about slavery, yet here we are. If fanned frets were standard and parallel frets were the outlier, the sides would likely be reversed.
To say the difference is "very" discernible is quite a stretch. As for the physics, like in many situations, what is true on paper doesn't always match in application. There are so many factors, from the wiring in your house that powers your amp to the thickness of your calluses, and the humidity in the air that effect your tone you produce and hear.
The majority of this discussion, as with most of it's sort is simple. Tone is 100% completely subjective and no two people will ever 100% agree.
As for the question, why don't more companies make fanned fret basses;
Using the transportation analogy - The P bass is like the average Honda, not too flashy, reliable as hell, easy and cheap to change and replace parts. Some drivers want more power, some want more speed, some need to haul around 6 kids(poor bastards and their dusty bass collections), and some want something that just looks outrageous and grabs attention.
Tesla doesn't make a minivan(yet), there isn't a Shelby Cobra on every street corner, and everyone hated the H2. The market dictates what companies sell and the largest manufacturers will always attempt to chase trends if they feel the investment risk/reward is worth it, but almost always fall short of what the boutique manufacturers were doing that sparked the trend. Most remember these past mistakes and are careful in the future.
The first Dingwall I saw was in the 1997 Bass Player Mag 5 String shoot out around 1997. The first fan fret instrument I ever saw. I remember thinking that it look goofy and gimmicky but also kind of cool. In 20 years, they continue to have the relatively infinitesimal % of their bass market covered and they do it very well.
As for Dingwall's low numbers and scarcity of availability? There have been almost a dozen for sale here on Talkbass recently and the relatively low production numbers keep the market strong and the values up.
In the mean time, I'll keep my eyes peeled for a 10 string Squire Stick.
