Well in banking, it's very important that there's trust in the system. Senior staff in UK financial institutions risk being barred from the industry if they're

Well in banking, it's very important that there's trust in the system. Senior staff in UK financial institutions risk being barred from the industry if they're found to have broken rules and there's a reason that kind of penalty is in play. Libor rates are quite serious as the outcome of trades depends on them. Each trade has a "winner" and a "loser" so if one side can choose the outcome they're essentially cheating the other side out of money. The equivalent would be going to a casino where they can arbitrarily change the odds of winning to suit them, during the game.