Can anyone explain cable risers?

The interaction that occurs is when something like a synthetic carpet has cables laying on them. The synthetic carpets properties are similar to those used in cable jackets and thus, compete with and interfere with those fields mentioned that travel with the cables signal. They simply smear the signal.

Yes, they can be measured so it stands to reason that if something is nearby, let alone parallel with and touchung a cable, can interact with it, then it can mess with it.

To what extent is debatable but if you have synthetic carpets, then go the extra mile to get them away from the carpet but you need not pay through the nose to do so.

I'm lucky in that my Mapleshade Double Helix speaker cables are so taut that they are easily suspended with nothing more than themselves and whatever nearby is handy.

If you have wool carpets or wood flooring, I wouldn't give it any consideration.

All the best,
Nonoise

"You can bet your bottom dollar that NONE of the various recording/mixing/mastering facilities are suspending their cables during the making of a recording."

I like that answer. All the recording studios I've worked in had the cables bundled together running across the floor or up inside a drop-ceiling. (We did keep power cables away from audio).
But I would agree with the theory to keep cables off the carpet.

Use gold coins below your cables and you will hear the improvement
immediately. Gold gets in reaction with the electrical field of the cables
and improves the molecular flow (more shiny). Some say, the best are
Krugerrands from South Africa ... but after long research I finally settled
with white-gold Rolexes below my cables. There is a swiss precision
added to details which is unique ...