I think looping was more common in older construction. Those devices didn't have the back-stab connections, so, if you wanted to avoid using a wire nut (because you had 3 hots and 3 neutrals to connect to the device) you had to loop the connection. I always thought that was a neat way to do it.
Now, what they do instead is to to use the back-stab and the screw. I've seen outlets where there was a wire under every screw and in every back-stab. That's pretty sloppy, I think.