Why do designers/manufacturers...?

I actually asked that question to two designers of electronics (major designers) --- each were uniform in their response. They both said re: power cords that power cords do not sufficiently contribute to the sound and, as such, they would not raise their costs by way of putting a "better" power cord on their product because it would not enhance the sound. The one designer (extremely well known)said it is an audiophile myth that power cords matter overly --- but that he designs now (like everyone) such that you can put an after market cord on if you desire. he said he does this "because those myths matter in what people are willing to buy... so because they want that flexibility... he would give it to them (even though it matters either not at all in terms of sound/or minimally in terms of sound)."

Designers are techies, for most if they can't measure it ,it truly does not exist for them. Their brain will not let
them hear it because the brain can not maintain a stasis
with such a reverse of foundation beliefs.

My elderly music lover brain lets me hear how PC x makes a DRAMATIC change in amp Y over PC z because it is in no danger of stasis instability.

In both cases it has very little to do with ears.

Peter Walker was an outstanding designer for his time.

A large number of audiophiles, to include reviewers, claim to hear noticeable improvements when stock fuses are replaced with "audiophile quality" fuses such as Synergistic Research Quantum Red and Audio Horizon fuses. Assuming the SR and AH fuses are not snake oil, then IMHO designers are remiss for not using them.

Because there cheap.