A Couple Little Things I'm Wondering About

Two quick questions for anyone with any experience with either topic.

1. Why do some folks with usually higher end systems use those cable lifters to keep the cable elevated? What are they intended to do? If you use them, what do they do for you please? And if you know do they make sense from a purely technical standpoint? 

2. I bought a bunch of those gold plated caps to cover all the unused RCA jacks on the back of my AVR. I believe they are intended to keep noise down. If you use these, please comment on them. Do you think they do what they're supposed to do, and/or do they make sense from a purely technical standpoint?

cable lifters: snake oil

RCA shorting plugs: will protect against noise interference that may possibly occur at the unused rca terminals.  Shorting them guarantees no signal, noise or otherwise will feed into your device.
If cable risers are snake oil, then why address vibration in you components at all?  Just what is susceptible to the floor-borne vibrations your system is generating?  
I've tried both since it doesn't really cost anything and yes it makes a difference.  Am I doing it now?  No.  Don't really care and not worth the trouble.  I would encourage audiophiles to try some of these tweaks even if they appear to make no sense.  If it doesn't cost anything what have you lost?  
@millercarbon has the best system in the world. It is certified by..(drum roll)..@millercarbon himself. If you follow his instruction you will end up not liking your system because your ears, head shape, room size and construction are all different. @millercarbon's system sounds better than anything to HIM!
Cable lifters can help separate speaker cables and interconnects from power cords, which can help to reduce or eliminate noise in your system. My previous system had issues when power cords were too close to other cables, so cable lifters helped to keep cables apart and the noise to a minimum.

Other than that, the mere fact of lifting cables off the ground does not lead to audible differences in my experience.

However, this is why I still use them:

1. Cable lifters prevent my robot vacuum cleaner from running over my cables. I use heavy ceramic cable lifters which do not budge when the Roomba bumps into them.

2. RCA caps keep dust and other particles away from my unused jacks, and I feel they also might be helpful in preventing oxidation.