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?

Thanks!