I think we are all forgetting a major contributor to audio products -- logistics. It really depends on how critical this specific area is to an audio manufacturer. If we are talking about somebody like ARC (Audio Research) who is so critical about these things that they have to use a specific brand/type of solder, then the selection of fuse can also be a major contributor.
Wyred 4 Sound used to advertise "upgraded Furutech rhodium fuse" in their DAC 2 SE level, so the boutique manufacturers that use specialty fuses are out there. However, Wyred now only indicates "upgraded fuse" without specifying type/brand.
When an audio manufacturer needs to have a board manufacturer build xx number of boards for them to use when assembling/integrating their audio equipment, they don’t want to worry about sourcing a specific fuse type. I have talked to a boutique amp manufacturer who never knows what kind of capacitors will be available for his main power supply when he gets ready to do a manufacturing run on his amp.
When the sub $10 fuses are readily available at industrial manufacturing houses (such as Little Fuse or Buss), it becomes very easy for them to just assembly and ship. These fuses are most likely sub $2 at this point and time is money. Even at the price point of Krell or Parasound, an additional $50-100 for a fuse will affect bottom line, especially in amplifiers or devices that have multiple fuses. I know the Parasound amps have a total of 5 fuses (that’s $250-500 dollars that affect the bottom line, which is typically 50-60% or retail). The additional time to order/unpack/insert custom specific fuses may also be a major contributor to a manufacturer who just wants to "get the amps out the door".