When Luke was writing his letters to Theophilus, it wasn't always just 2nd and 3rd hand research that he had sought out and included in the story, he was a part of the story too.
Even though I knew this, I don't think I've ever noticed the subtle change in the middle of Luke 16, when all the pronouns changed from 3rd person to 1st person. It changes back to 3rd as Luke apparently stays behind in Philippi, but in chapter 20, Luke rejoins the story in person.
Maybe not as valuable as actually knowing the Gospel, but still adds a kind of realism to the whole story since he is telling first person experience.