From Wikipedia: a skeuomorph is "an element of design or structure that serves little or no purpose in the artifact fashioned from the new material, but was essential to the object made from the original material"
The gradient and shadow on buttons are not just ornamental, they serve the purpose of conveying depth, and consequently that they afford being pushed (also, real-world buttons are usually a solid color).
From Wikipedia: a skeuomorph is "an element of design or structure that serves little or no purpose in the artifact fashioned from the new material, but was essential to the object made from the original material"
The gradient and shadow on buttons are not just ornamental, they serve the purpose of conveying depth, and consequently that they afford being pushed (also, real-world buttons are usually a solid color).