Why did Jesus have 12 disciples but not all have written their gospel?

 

Simple. Not all 12 disciples wrote gospels. At least one of them (Judas) hung himself before he could have written a gospel.

Of the 4 gospels that were written, only two of them (Matthew and John) were written by one of the 12 original disciples.

Mark was a teenager at the time of Jesus’ ministry. But his family were followers of Jesus but not “disciples” and it was in his (parent’s) home that the Last Supper was held. Mark was present for most of the events of Jesus’ ministry, and even appears as the “young man” whom the mob that arrested Jesus sent fleeing into the night naked. Mark first traveler with Paul (who did not know Jesus during his earthly ministry) as a witness to the events of the life of Jesus. And later he also traveled and was mentored by Peter. His gospel includes both his experiences and what he learned from Peter.

Luke was a Gentile covert under Paul, and did not have any first hand knowledge of the ministry of Jesus. As stated in his gospel, everything he wrote was because he was able to find the people involved and get a first hand account of the events. His gospel has some variants from the others because if he could not find an eye witness he did not include the event or some of the details of the event.

If you were a historian, there would be four kinds of accounts of a person that you would like to find. One would be from someone who was part of the inner circle and had first hand knowledge of both the events and the person. You have that in Matthew. You want an account of someone who witnessed the events from “outside.” Who was not part of the inner circle, but would show you the public face of the person. You have that in Mark. You would like an account from an historian who researches the facts and interviews the witnesses. You have that in Luke. And finally you would want an account of someone who was part of the events, but writes about years later being able to view them through the lens of history and legacy of the events and their influence on history. You have that in John.

There are other books that claim to be gospels by other disciples. But there is zero evidence that these books were written anywhere close to the lifetime of the disciples. They do not appear until centuries later.

Currently there are over 2,300 known copies of the New Testament texts in the original language. There are usually only 1 known copy of these “other gospels” and several do not have even a single complete copy. There are dozens of collections of the gospels in a single scroll (the book had not yet been invented.) They all contain only the four gospels we know today. (Some also include the book of Acts.) Not a single collection include any of these other gospels.

The four gospels can be completely reconstructed from quotes in other writings by the early church fathers. Not a single quote has been found anywhere from any of these other gospels.

You may have noticed the Dan Brown’s book “The DiVinci Code” is not found in the Bible. Even though it claims to have a history of Jesus. Because it was not written by any of the apostle (there are 23 apostle besides the original 12 disciples listed in the New Testament) nor dates from anywhere close to the lifetime of Jesus. Plus we are close enough to when the book was released that we know it is not real.

Same with these “other gospels.” They were not written by apostles. They were not written anywhere close to the actual lifetime of Jesus. And the people who selected the books that would be in the New Testament knew they were not real. (And many of them did not even exist yet when the canon of the NT was settled.)

The reason that there are not 12 gospels, one from each disciple, is that not all 12 of them wrote anything. And there was no reason to tell the same events 12 times. the four we have covered the events from the four main viewpoints that you would want for a historical event.