Thinking about it as a modern person that makes sense. All sorts of people tell all sorts of stories about a lot of things. But in Jewish society that didn't happen. One big reason was the Jewish law about false prophesy. False prophets were to be executed. How could you tell a false prophet? If the prophet predicted future events based on revelations from God then if one of those events did not come to pass he would be known to be a false prophet. It was very much a one strike and you are out policy. If you claim God told you that X will happen then X better happen or you forfeit your life.
If you think about Mary's story with the angel. Did she predict a future event? She did. She said that she was going to give birth to a son. What if the child was female? Beyond that, the infant mortality rate was pretty high back then. What if the child died? Would that not put her in the uncomfortable situation of having made a prediction in the name of God and having it not come true?
Could she really be executed? It might depend on how widely know her prediction was. We don't know how public she went with her story. She told Joseph. She told Elizabeth. Once you tell a few people a story like that is pretty hard to keep quiet. Could a woman be executed for false prophecy? I don't know. Women were referred to as prophets in the bible. It makes sense that they would be subject to the same rules.
None of this comes across in Luke. Why would it? These calculations are for those telling lies. Truth tellers don't worry. If you really saw an angel then you would not worry if what he told you was true. There is no evidence Mary was worried. But the idea that this story might have been Mary's way out of an awkward situation is a little harder to swallow.
If you think about it, future events lined up so well with Mary's angel story that it can build our faith. If you don't look at the story as a skeptic but as an honest seeker of truth. When you see the mothers of celebrities interviewed what do they say? They don't make up fancy stories of amazing circumstances around the birth. Nobody expects them to. It would be the same for Jesus. When Luke interviewed Mary he was not looking for something amazing. There was no reason to make anything up. Christianity was already growing.
It ends up being one more thing for skeptics to dismiss based on a vague conspiracy theory. Either that or it ends up as one more witness to the historical truth of Jesus. Maybe Mary is the one witness who you will find convincing. They say nobody knows a man like his mother knows him. That is certainly true of Jesus.