That's because it is unusual to see people reacting and moving that fast
That's one of the thing that impressed me when they first showed the super speed. Is it perfect CG? No, but it's pretty damned cool looking to me
That is one of the things I like about this movie, how they can depict superspeed. I think it looks very good. It is one of the things that bothered me about the Reeves movies. Due to where technology was at the time they really couldn't show superman moving at fast speeds.