Is That a Reasonable Question to Ask?

Zachariah and Elizabeth get married. They pray like every other couple, especially at that time when to be barren is to think you're somehow cursed by God. And then here comes Gabriel and says, your prayer has been heard. Zachariah is like, well, how in the world is this going to happen? When I pictures the angel Gabriel saying to Zachariah, then why did you bother to pray if you didn't think God was going to come through?