Answer the question about text:

And the whole multitude of the people was praying outside at the hour of incense . hen an angel of the Lord appeared to him , standing on the right side of the altar of incense . And when Zacharias saw him , he was troubled , and fear fell upon him . But the angel said to him , " Do not be afraid , Zacharias , for your prayer is heard ; and your wife Elizabeth will bear you a son , and you shall call his name John .

What may be the reason for praying in desperation ?
They were longing to be a father .