Because the models become a database you can search for certain characteristics.

(This is a guess I consider reasonable.)

Its somewhat complex. Protein structures are usually solved with x-ray crystallography. You get a 2-dimensional diffraction pattern. There are different methods to "solve" the diffraction pattern and get the Protein structure. Most are a lot of work, including biochemical lab work. But if you have a model it is relatively easy. The modern computer generated models have revolutionized protein x-ray crystallography.