Low and high carbon steels are both used for drill bits, but for different purposes. Soft low carbon steel cannot cut hard metals due to their poor tempers, but they can cut wood. They require sharpenings to extend their lifespan. The primary bonus of low carbon steel is its relative inexpensiveness, especially when compared to some more exotic drill bit materials.
High carbon steels have better tempers than low carbon steels, so they require less maintenance, such as sharpening, and hold their form and effectiveness longer. They can cut both woods and metals, and if available, are preferred to low carbon steels when cutting extremely hard woods.