Does "waxing" the bottom of sled rails or snow skis make for a faster ride?

For years, my family has always had a package of Gulf Wax in the garage. As a child, i would look at the package and ask myself, “what the heck is this for”? Finally, one day my dad and I were together in the garage and I asked him this question. He told me the wax, applied to the rails of a sled or snow skis, would make them glide on top of the snow, for a much faster ride . Question: was this theory true? Does anyone still use wax for this purpose and does it actually work?