Why. 90% of it is going to be artists being self-conscious about critique or people getting rid of opinions that don't agree with their own.
I liked that FA was one of the sites to not have this feature because it meant we were at least one small step away from murry purry hugbox central. Why not spend the time on, I don't know, the new interface? Or making sure comments thread correctly god dammit.
\I am grateful for the work that the coder(s) put in though, don't think otherwise