Why didn't Johnny Sack just whack Ralph?

Why did he ask for permission in the first place? Why didn't he just hire someone to kill Ralph without telling anyone? If he would've been asked about it he could've always said "it was a terrible accident, I don't know what happened" and just stayed like nothing, no involvement could've been proved. He would have been known as a fearless mf, someone you don't want to mess with, while taking no blame.

At the moment he complaint to Tony and to Carmine he started the "gears" of chain of command, he lost his chance to have Ralph paying the price and to repair his honor.