The truth is we don’t know the answer to that question. It would be great to discover some long lost letter by Jesus. However, it is unlikely to happen.
I do have some thoughts on the subject. I definitely don’t think that it is a condemnation of writing. The fact that the Spirit inspired the apostles to write the New Testament is evidence against that.
I suspect that real reason that Jesus didn’t write a book is that Christians would worship the book rather than the author. Many Christians have trouble not doing that the way the Bible is. If Jesus had written the New Testament it would be almost impossible to keep our eyes on Jesus. Having a Bible that is divinely inspired but written is a symbol of how God uses us for ministry.
- Jesus Christ
