Contact lenses are favored by around 30 million people in the United States for vision correction, because you don't need to wear eyeglasses. People choose to wear contact lenses for many reasons, often due to their appearance and practicality. When compared to spectacles, contact lenses are less affected by wet weather, do not steam up, and provide a wider field of vision. They are more suitable for a number of sporting activities. (Contact Lenses Wiki)
Contact lenses are a completely different product than eyeglasses, which explains why Eyeglasses.com does not offer contact lenses. You can get contact lenses at your local optical store, or at a number of stores selling contact lenses online. Here is a website where you can compare contact lens prices.