yeah but arent our computers so buff these days that this is unecessary
For anything you and I are likely to do, yes.
Looking at folding at home, though - your average protein has between 100s and 1000s of amino acids, each with a few dozen atoms in it. Even so, figuring out the electron density of an unfolded protein would not be such a big deal for a modern computer.
But those desnities put forces on it and start it to folding, so things redistribute, so the shape changes, so things redistribute. Oh, and add the effect of an aqueous environment (your insides). While you're at it.....