My guess is to reduce overhead since there really isn't any sensitive information being entered (financial/personal). According to a question in StackOverflow. >So for large files it's negligible, but for small files can be significant, as pointed out by Eugene.<
Not a lot of pictures hosted directly on the site, low bandwidth requirements. Servers run kinda slow to begin with. Probably some brilliant SOBs on tropical island [
www.youtube.com] accessing through satellite too