Why don't amplifier Companies use high end fuses?

Two kinds of fuses - power supply fuses and those in the signal path (output fuses).

Never heard a difference in power supply fuses.  If you do, great.  Something else to spend money on.  Maybe it's just because I use amps that run for about 20 seconds after switched off before you hear the sound get congested and then finally end about another 20 seconds later as the caps drain.

Output fuses are a different matter.  Doubt many of you have seen or even heard of the speakers I use in my 3rd system - Vandersteen 4a. In writing the manual on those Richard Vandersteen advocated getting rid of any output fuses and replacing them with 1/4" solid copper automotive fuel line.  Not sure amplifier manufacturers would approve, but those fuses are directly in the signal path, and if you believe that speaker cables make a difference, you pretty much have to agree that the inch or two of fuse in the path also must affect sound.

@koost_amojan,
This is beginning to sound like the "all cables sounds the same" argument, or "all amps, designed correctly, sound the same" argument. 
They measure the same, or close enough, so how can you hear a difference?

Are you in that camp?  Another lost cause. As for your remote diagnostic abilities as to my being easily fooled, all I have to say is you missed your calling. The CIA could have used you for remote viewing, spying on the Russians. I hear they pay well.

As to the ability to measure black holes, if NASA, with all their resources, decided to investigate the differences between fuses, they's find it in the first round of testing.

As for measuring, I had to turn down my volume by 2-3db because after changing directions, it was too loud. Also, I had to turn off the treble boost and go back to 'flat' since the highs were now restored. That was measured by my ears. Delusion had no part in it. That's all I needed to convince myself. What have you done?

All the best,
Nonoise

Under transient loading and a traditional power supply or rectifiers, caps and transformers..the fuse is definitely in the signal path.

And it carries import due to the fact that the ear/brain derives 100% of what it hears, via 10% of the signal -----which is that of the transients. Just the transients. Just the leading positive edge, in their value, with respect to one another, and the timing between them, as a group.

The ear does not hear or use the other 90% of the signal. Which is why engineering weighting in signal analysis, where 100% of the signal is used..is mostly in error when it comes to correlating those engineering numbers to what people hear.

The ear is a balls on -off the rails- impossibly complex ~impossible to replicate with human hardware~...FFT analysis device. Far finer and more refined than anything we can build.

BTW, FFT analysis is based on quantum holography. No joke, no woo-woo, no hyperbola. That’s where the math and method of FFT comes from. It’s where FFT really shines.

The takeaway or next domino of logic (much research in this area for the intrepid explorer of science to find and peruse) Is that the brain function is Quantum zero point energy based - non-local holographic.

Ain’t that a peach.

Point is, that most people arguing science here, don’t even know what the heck the car/vehicle that they drive and live in ---is.

No woo-woo, this is good solid modern cutting edge science I speak about.

A bit of extra point/credits, is that we’ve even had scientists remove part of the brain from animals and the animal fails to function. Which is expected, yes? Then, as an extreme level finale... to try and get to the bottom of their results..which will become clear in a second (regarding their high strangeness)..then take the half of the brain that was removed, grind it into hamburger(!)... and stick it back in to it’s original spot..and the animal goes back to functioning normally. In that context, what exactly is a brain, then? (No one exactly knows yet, but it’s certainly beyond classical Newtonian meat and clockworks, as the intrepid seekers have found out.)

Ouch. Definitely one step too far for the fears of most humans. Not unlike that of this ridiculously simple question about fuses.

When we look at how the world ~really~ works, it can drive the intelligent to tears.... to see how uninformed and unaware people can be...and then...argue about such trite and obvious stuff as whether a person can hear a fuse or not.

@teo_audio,
Bravo!

By the way, how many patties can I get out of half my brain? 
Apparently, I don't need it anymore, and I loves me a good burger. 🤔

I thought I was asking a simple question but given my email account is  exploding, I think I opened up a can of worms.