Does raising speaker cables off the floor really make a big difference?

All depends on 1. whether the carpet is wool or synthetic; 2. the carpet's warp and weft; 3. which direction the fibers are vacuumed in vis-à-vis the cables lying on them.

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.

I have to go wit the "made no difference at all" crowd. I have tried this in my systems as well as having others I know try it. Not many of us as there were only four total but not one of us heard a difference. And if there was actually some difference it was not audible, and certainly not worth the price of any expensive cable elevators. The most common method used were wood blocks, and all of us tried the Cardas elevators. Again, like everything audio, it is so system, room and home  / environment dependent. One just has to try it on their own, or get enough feedback from places like here to make your own informed decision.

"3. which direction the fibers are vacuumed in vis-à-vis the cables lying on them."

If you have not been vacuuming in circles, you have been doing it wrong all this time.

Well shoot!
That's why I have crop circles in my deep shag pile!

😉😉