I have limited experience but I understand the real reason for using them is to keep the bag clean/er. Seems like they would most be welcome on a long thru hike like the AT.
Perhaps a very light set of long sleeve/ long legged underwear might take its place while serving another function.
But...a big but, is what happens when the weather is hot and you want to be naked?
And what about the twisting about your body question?