Because this game is fucking broken, that's why. It's almost one year old, and it still has major issues.
I got pretty frustrated today because of two major things that need to be fixed:
1) Most of the time when I want to subdue someone, I just puch him in the face instead. Other players have been complaining about this for a while, but it still hasn't been fixed.
2) Pistol headshots aren't fatal most of the time. I went on a killing spree today, but most of the time when I shot someone in the head with my Silverballer, they don't die.
IOI, fix this shit please. This game is almost one year old, and it still doesn't feel polished.