Here's why:

* Compression: Folds occur when rock layers are subjected to compressional forces. These forces squeeze the rock, causing it to buckle and bend.

* Upward Displacement: The bending of the rock layers often results in the formation of upfolded areas known as anticlines. These anticlines can form the core of mountain ranges.

* Examples: The Appalachian Mountains in North America and the Himalayas in Asia are prime examples of mountain ranges formed by folding.

While folds can also lead to the formation of other geological features like valleys and plateaus, mountains are the most prominent and widespread result.