"Amplifier manufacturers don't have a clue"? That is just not true.
The costs of many of these "audiophile" fuses are pretty high. That would be added to the costs of the equipment sale price. also, if the equipment sounds pretty wonderful with stock fuses, I would leave it to the buyer to fuse roll. Same is true for tubes. I would chose some tubes that suit my equipment. Sell that equipment with that tube set. I'm sure there would be tubes out their that offer different sound characteristics. But, the "consistent" great sound I want from my equipment is reached using the tubes my company would supply. Same is true for fuses.
So, if a buyer wants to change tubes and tube roll as it were. More power to them as long as it doesn't hurt the equipment. Same is true for fuses. As long as the audiophile fuses are at the same voltage/amperage rating as the fuse they are replacing.
But don't believe the hype that manufacturers don't know about audiophile fuses. They do. Lots of reasons why they don't use them.
People on this forum and other places constantly complain about the high costs of audio equipment. Specialty capacitors costs. Same is true for great resistors and other components. Some not off the shelf. Add high prices for fuses to that mix? wow! A fuse. I'm sure it may make a difference. But first, how does it sound with regular off the shelf fuses? Pretty darn good? Then no way would I install high price fuses.
I just wouldn't.
Let the buyer do that if they want.
enjoy