I don't know but I feel more balanced or stabil when I have my feet up on my highway pegs. I don't know what really. My best quess would be for the same reason tight rope walkers use a long pole. For the most part I would be happy to completely remove my boards and install controls off of my highway pegs. LOL.
I am pretty tall so usually I throw the back of my boots up on the highway pegs other wise it looks like I am on a mini bike but I do ride a Road King..
I don't know that I feel more balanced and stabile, but it does let me relax a bit and change my riding position while riding. Just have to be aware that I could get too relaxed so I need to keep my guard up. I wouldn't be without them for long trips, that's for sure.
I like mine too. But we take a bit of a risk with our feet out of position in relation to the rear brake and shifter. I use them on interstate runs but never in congested traffic.