First ran across it in D&D when I would announce, while we rolled up characters, that I was willing to play the cleric, and lo and behold always got to play the cleric. (Indeed, I could sometimes get some really interesting stuff because the DM wanted to keep me happy because -- I would play the cleric!) The commonest reason was that they didn't want to play a puppet. No matter how long they had played in the same group as me, merrily playing along with motives and all that stuff. . . .
But it was not helped by the D&D stuff, which tended to the nice people have nice gods, and not-so-nice people have not-so-nice gods, and that's a tendency in fiction as well. Indeed, just read a good chunk of a novel where a major plot development was the conflict between two religions and all we know is that one has nice people following it and the other one has not-so-nice people.
Then, why would a nice -- Lawful Good if you will -- priestess serve a nasty -- Chaotic Evil if you will -- god -- say a storm god? Well, the most obvious is to keep the god happy. A woman who had lost a number of relatives in a sea storm would have every reason to want to appease the storm god. Particularly if she still had living relations who went to sea. And there is the trivial little detail that he is, after all, the storm god. Any mortal is going to know it's not likely that's going to change. A Lawful Good one would respect the proper, ordained order of things that put this god in this place.
Then, that ties into another aspect: the gods don't have motives. Keeping the gods happy is an important thing because if they are not kept happy, they can act. But a lot of world-building on religion does not touch on how the opinions of the Powers That Be are not a minor consideration when deciding what to do.
I wonder if this is an element in having the Chosen One always get blind-sided by the choice. After all, if the Chosen One had to work for the honor, there would have to be a powerful reason why. Pure devotion. Desire for revenge, or excellence, or what have you. But you have to give some motive, and that's not a strong point in many scenarios.