For the rest of us, copying figures from 2-dimensional sources is a cheap and easy alternative. Some illustrators compile scrapbooks. Some animators cover their walls with visual references. Some artists take landscape photographs specifically for their paintings. Rembrandt made copies of Leonardo's paintings and incorporated the studies into his own paintings.
Copying is a means of learning.
You learn how to look at and render the human figure, fabrics and armor. You can study the details in different textures, forms, shapes, materials and shine in objects. You can take note of the colors and compositions used in other pictures. You can experiment in styles and techniques, or also just use the pictures to stimulate your own imagination. Even tracing, which I've always been personally biased against, has been argued in The Artist's Magazine as an effective means of learning to draw, because one is training in tracing images mentally while tracing images physically.