Judging from the Internet, most modern guitarists sneer at folks like Jack Gentul because they didn't make it big. The assumption seems to be that if someone has built an excellent product, lots of people will purchase it; if they don't, the product must be inferior. That assumption rests on another assumption: that people know about the product, try it, and reject it on its merits. But what if they don't even know the product exists?
Jack Gentul did not have control over how his amps were advertised or distributed; that was left in another, more powerful person's hands. And that person was not interested in making any substantial investment in Hilgen.
I have possession of a distributor's catalog from about 1966. The distributor, "Music Distributors, Inc.," was from Charlotte, North Carolina. This company apparently had the account for distributing Hilgen Amps. The other products in the catalog are execrable. Unbelievably hideous, low-priced guitars and amps. If I'd run a music store in the mid 1960's and someone had handed me that catalog, I would probably have thrown it away either (a) without reading it, in which case I would never hear about Hilgen amplifiers, or (b) after reading it, in which case I would assume that Hilgens were junk and nothing I'd want to sell in my store.
And what about Elmore Heppner?
But that's another story...