As a kid, I used to read Greek legends like it was going out of style and a big feature in some of their tales was the concept of fate and destiny as an unavoidable thing. And that many legends occurred simply because one person tried to do something to shirk fate.
I imagine with the oracles one of the reasons they tend to be rather vague with their information is because there is a balance between destiny and free will and there is something to be said about the discovery of the answer than simply being given it. Not to mention being too flippant with answers would end up with those types of people who like to come up with catch 22 scenarios and would try to get a prediction just to try to break it. As that tends to be a big feature in modern day concepts of fate and destiny.