Static electricity can be caused by friction, electrostatic induction or electrostatic conduction. I am no physicist but it appears the static phenomena between the wire and the carpet fibers is caused by either induction or conduction.
Charging by conduction involves the contact of a charged object to a neutral object. In contrast to induction, where the charged object is brought near but never contacted to the object being charged, conduction charging involves making the physical connection of the charged object to the neutral object.
I’ll leave it to others to determine which is the cause. FWIW, static is more likely to exist in a drier climate versus one that has higher humidity. That may be the reason some experience no sonic impact from elevating the speaker wire from the carpet.
If you some cd’s, you can try this simple experiment (raise wires off the floor with the case) for $0.00 and a couple of minutes of your time and determine if you can hear the difference or not.