Steve Ray has a list of 35 loaded Questions for "Bible Christians" (quotation marks his)(link to the whole list). This is number 28/35. I'm trying to provide the answers in a common format, for easy reference.
28) If Jesus intended for Christianity to be exclusively a “religion of the book,” why did He wait 1400 years before showing somebody how to build a printing press?
ROFL [Quick note, one reader has pointed out that laughter has been the answer for the last several questions. The reason is that some of the questions are rather absurd. This is one of the most absurd. The longer answers below in the qualifications section should provide meat that no simple answer to these kind of absurd questions could provide.]
1) This is a variant on the old "If God had wanted us to fly, he would have given us wings" argument. It is as absurd as that one.
2) But more seriously, we don't know God's exact reason, he hasn't told us.
3) One possible reason is that one's memory is aided by copying out the words of Scripture by hand. Thus, for example, the kings of Israel were given the following command:
Deuteronomy 17:18 And it shall be, when he sitteth upon the throne of his kingdom, that he shall write him a copy of this law in a book out of that which is before the priests the Levites:
4) But why stop at the printing press? Why not demand that God give the 1st Century a photocopier or Google books?
5) More to the point, if images of Christ are acceptable and if oral tradition is so important, why not have ever second of Jesus' incarnation recorded for us in 3D video with 7.1 surround sound and subtitles in our various languages? Or better yet, memory implants so that we all have a complete photographic memory of the entire ministry of Christ? But all this is absurd. We don't dictate to God how he carries out his work. We should be thankful he did give us his Word in the scriptures of the Old and New Testaments rather than asking vain and unanswerable hypothetical questions that would require us to have a knowledge of the secret counsel of God.