Don't know how much "thriving" is going on, or why you are "puzzled".
After all, you're also talking the same "country" that has allowed the company proper, JBL, to die a protracted, painful and rather undignified death (as compared to it's former self and vision).
I just very recently required the services of an expert brass musical instrument service, as in capable of an all under one roof service capable of delivering impeccable results a for fine, rare and collectible horn. I was in need of a complete rebuild as well as a new lacquer finish.
It doesn't exist, although with at least ONE sublet (the lacquer) my goal was accomplished with reasonable results. It took almost 1 year to get the job done. Probably Wynton Marsalis doesn't have these problems, but the rest of us (the unwashed) do.
Plenty of SUPERB "one stop shop" luthiers though, thanks primarily to Nashville, Tennessee!
It is a "new world order" in the good old U.S.A. and that's just the way it is. Not saying that such a service does not exist or cannot be had, I am saying that if they're out there they keep a very low profile.