Why Do Cables Matter?

To me, all you need is low L, C, and R. I run Mogami W3104 bi-wire from my McIntosh MAC7200 to my Martin Logan Theos. We all know that a chain is only as strong as its' weakest link - so I am honestly confused by all this cable discussion. 

What kind of wiring goes from the transistor or tube to the amplifier speaker binding post inside the amplifier? It is usually plain old 16 ga or 14 ga copper. Then we are supposed to install 5 - 10' or so of wallet-emptying, pipe-sized pure CU or AG with "special configurations" to the speaker terminals?

What kind of wiring is inside the speaker from the terminals to the crossover, and from the crossover to the drivers? Usually plain old 16 ga or 14 ga copper.

So you have "weak links" inside the amplifier, and inside the speaker, so why bother with mega expensive cabling between the two? It doesn't make logical sense to me. It makes more sense to match the quality of your speaker wires with the existing wires in the signal path [inside the amplifier and inside the speaker].