As someone who has given scores of a "3", I will give my personal reasoning. I consider a "3" to be average, which is a well written story and to be expected. I don't consider a "3" to be a sign of failure on the part of the author. For a story to receive a "4" from me, it has to be above my expectations and a "5" requires an almost emotional response when I read it. If writers find my scoring too harsh, too bad. I have received messages from writers who I have given a "3" and I explained my reasons. I have also been blocked by a few so I can't score any more of their stories. Personally, I think a number of writers on this site are very thin skinned individuals. I'm sure their vanity will let them know exactly who they are. I don't think I've ever given a story a "1" and I have rarely given a "2".
Maybe it was my education in the school of architecture that made me realize that "average" is the norm. To be above average is what we always strive for, but it's usually not achieved - at least not in the eyes of the viewer.
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