Luke 1

Luke starts his gospel by giving his purpose:

Inasmuch as many have undertaken to compile a narrative of the things that have been accomplished among us, just as those who from the beginning were eyewitnesses and ministers of the word have delivered them to us, it seemed good to me also, having followed all things closely for some time past, to write an orderly account for you, most excellent Theophilus, that you may have certainty concerning the things you have been taught.

He is writing to provide a record of the eyewitness testimony of the people who saw Jesus grow up, those who walked with him daily, saw him die on the cross, and saw him resurrected from the dead. I think the closes thing we have today would be a journalist. He is invested deeply in the story, to be sure, but his purpose is to report the story as he had gathered it so that those people who had not witnessed these things could know the story and have confidence in the key events surrounding their faith.