The logic of interconnect cables?

This question has always been with me...without a satisfactory answer to date.

Why do we not use the same internal wire ( for interconnects) that manufacturers use which feeds their outputs or inputs internal to their product?? It would seem to me that this wire's quality (regardless of what we use eternally) is a limiting factor in the first place

Example..I have an ARC Tube Preamp and ARC tube amps...why do I need "special " interconnects when in fact, the wire used to feed the output of my XLR preamp output is the same identical wire beyond the xlr input of my amps?

I would appreciate some logic here.....Thanks