Ski pants are usually 4-5'' longer than your normal pants because when you go skiing, skiers need to wear snowshoes.
The ski pants should be long enough to cover the snowshoes. then will keep warm for skiers and avoid the snow infilter inside the leg. at the same time, It also provides protection from the wind for skiers.
You can imagine if ski pants were the same length as your normal pants, can not cover the snow shoes, when you skiing, the snow will go into your inside leg & shoes then get wet easily.
