Here are some thoughts, take them or leave them as usual....
I think that when a person goes through a process of training, and 'get up the nerve' to practice evocation and such, their worldview and attitude is vastly different than a person who does the traditional 'begging for mercy', seeing themselves as lesser than the being they are asking for protection. A person who is traditional-minded will think themselves as powerless and, if they are religiously inclined, they might even see themselves as undeserving of that help-if you look at some religious prayers you will see this attitude reflected. So in my view, the entity (whether it's an 'honest-to-goodness' archangel or an universal energy 'thoughtform') will respond not just to the expressed desire but to the implied feeling- which may result in either a weak amount of help-feedback or no help at all, while the magician who has the feeling of control of the being may have better results- because they know they deserve the help or believe that they do.
Of course, this is just one possibility.