Manufacturers past their heyday

I think the answer is very simple.  The heyday of consumer audio was from the late 60's through the mid-80's.  The manufacturers who developed a loyal following then and have continued to produce equipment that appeals to that following remain.

A speaker I owned and thoroughly enjoyed in the past was Jantzen.  I had the 412A model of speakers.  They had a 12 inch woofer and 2x2 array of electrostatic elements in a sealed box.  The company is still around and is now run by the son of the original owner.  I have not heard a current production model.  I would love to hear them, however, they are way out reach of my retirement income.

That was Janszen, sorry, I had forgot the correct spelling.

No highs? No lows? Must be Bose!

There are several factors at play here. One, many of these legacy companies have been absorbed by big conglomerates (Mark Levinson, McIntosh, Harman Kardon, and Martin-Logan come to mind immediately) so they're no longer driven by a few brilliant guys passionate about delivering the best audio possible, regardless of how much profit they can squeeze out of every unit sold. (And, a lot of the legends and pioneers of high-end audio are no longer with us, Those geniuses were the drivers of their brands. Without them, many of their brands are shadows of what they once were.) Two, audio technology hit a plateau years ago. There's only so much audiophile-worthy innovation that's coming forth nowadays, unlike during the golden age of the 70-90s. Three, digital. Streaming audio has more or less killed the notion of audiophile sound. Convenience over quality. Then again, it has driven the vinyl renaissance, so there's the silver lining.