Ski skins aren’t exactly a new invention. The first skins were used by the Inuit people for their dog sleds. The sleds also provided the basis for modern skiing, showing that a body put on skis could be more easily maneuvered over snow than a body walking. They used seal skin over their wooden sled skids (which was the word later shortened to skis) to help grip the snow and prevent the sled from moving backwards.
That principle was the same one that cross-country or touring skiers were after to make their lives easier. A ski, waxed or un-waxed, will slide backwards and forwards equally smoothly. This is ordinarily not an issue, as a downhill skier runs very little risk of accidentally sliding back up the mountain. However, ski touring tends to require several segments of climbing in a trail. This was difficult for skiers, as their skis would try to take them back down the hill at any opportunity.
So while you won’t see many ski skins at a resort, they are an invaluable asset in the backcountry. The next time you think that the slopes at your local ski area are a little crowded, entertaining the idea of backcountry skiing might not be such a bad idea. It takes some dedication and skill to become a good backcountry skier, but the rewards are well worth the effort.