TL;DR Because capitalism, mostly.
This isn't really unique to capitalism - it's just politics and interpersonal competition.
This kind of thing happened in the Soviet Union, it happened in monarchist France (court of Louis XIV), it happened throughout all of human history.
Because blame goes down, and reward goes up, so its a lot more important to make sure that the blame for wrong doesn't get to you than to make sure you get the credit for right, since the reward for right is an "attaboy" where those above you reap the substantive benefits, while the punishment for wrong remains substantive.
TL;DR Because capitalism, mostly.