Surely there are itineraries that are within the reach of beginners and amateurs, so risk management is not necessary. Having said this, especially in the high mountains, there are many variables and pitfalls that a guide is accustomed to evaluating and keeping under control, unlike an “occasional” or amateur visitor, who does not have the same critical vision.
Imagine, for example, an unexpected or sudden change in weather conditions and consequently in visibility… the situation immediately becomes more complex to manage and the guide has the skills and technical preparation to get out of that specific problem.
The same considerations can be made in case of management in emergency situations (e.g. avalanche, fall into a crevasse, injury on the wall, etc…)