Indeed, Paul's use of these pagan verses, along with the line of continuity he draws from the altar to the unknown God to the God known in Christ, parallels his treatment of Old Testament characters, events and verses as types of a greater revelation to come.
The same reason that we look diligently into the Old Testament for glimpses into the truth of Christ's coming and the Gospel, we can look into true pagan literature for the same. That seems to be what Paul understood in Acts 17.
