That’s like asking why if I believe miracles are possible why I don’t think Doctor Strange and the marvel universe is historical. It’s because the textual and historical evidence is against it.

Jesus might have been a real person (the majority of scholars do believe this), but there is an overwhelming amount of evidence that suggests the bulk of the stories are told with a purpose other than an historical account.

I grew up Christian, went to a supernatural school of ministry that focussed in the miraculous, and eventually became a traveling minister. I’ve seen miracles. More than most people would believe. I don’t need the Jesus story to be historically factual for me to know those things are real. Because I don’t rely on it for that belief, I can take a more skeptical view of the text. When I did that, it just didn’t stand up to deep scrutiny.