True, but the price of risk management also plays an important role. And the price of the guaranteed insurance is horrific over many trades, far more than if the trader accepted the slippage (which may of may not come, and if it does is often not bad at all).
By all means use a guaranteed stop on a few trades here and there for whatever reason but to constantly use them is a sure fire way to effortlessly transfer one's cash balance to the spread bet broker, and that's why the client that uses them a lot is going to become a very 'valued client'.
Forget owning a Casino, I'd like to be the one underwriting the risk on all the guaranteed stops, talk about a licence to print money overtime.