Why does an audiophile grade power cord matter?

probably another beaten horse topic but I cannot find answers to quell my question.

Basically, most of us have homebuilder standard supply solid core copper wire with nylon, plastic or rubber sheathing that runs the length of our homes from some cheapo metal utility company supplied junction box to a 5 dollar leviton outlet Joe General Contractor buys at Home Depot. So the current at that 5 dollar outlet is what it is until we hook it up to our system.

So why does plugging in a 1.5 meter or what ever length of audiophile grade xxx hundred dollar power cord matter to go that last couple of feet to our components???