"Jesus performed many other signs in the presence of his disciples, which are not recorded in this book. 31 But these are written that you may believe" (John 20:30). What I have taken from this verse is that God has chosen various signs that a reader can look at and make a decision to believe among the evidence that was given to us. So, that's why some of Jesus' signs ended up being recorded in the book while others were not, As it was mentioned later in the scripture, there are way more things Jesus did that didn't get recorded so I can only imagine it was a matter of choosing the best ones helping one end up believing the things Jesus had accomplished in order for people to show their faith.