Maybe, but there is that instulation to help protect the boss. The boss gives the order to kill someone, the capo picks a soldier to do it or the soldier picks an associate. Scarfo comes to mind, but he did not pull the trigger, he was only present in the apartment when it took place. Casso killed Hydell personal, but he was not the boss, but an administration member in the Lucchese crime family. The Irish bosses on the other hand have been known to personal kill instead of having an underling take care of it.