Luke wrote an account of Jesus’ works and the message of His Apostles. He wasn’t trying to give a medical diagnosis when he wrote to his patron Theophilus. Luke, it seems, was loaned to Paul for his personal afflictions and ailments. Since he was an investigator and literate, he could describe both the accounts of the witnesses of Jesus and relate his personal travels with Paul ministering the word. Neither of these accounts would resemble medical documents (Luke was there to minister to Paul, not to sharre medical knowledge with Theophilus).

Since the publishing of more complete databases, Luke still probably sounds more like a physician than previously thought.

https://www.tyndalebulletin.org/article/133200-luke-the-physician-some-notes-on-the-internal-evidence