There are reasons for the different gospel authors including what they did (though we can only speculate what those reasons are). For example, Matthew included the naming of Peter as the Rock, but Mark’s gospel (which Peter is said by some to have dictated to him, if I remember correctly) doesn’t include it, and one explanation is that Peter was too humble to want to mention it himself, so Matthew’s gospel includes it.
John’s gospel is the only one which contains the Bread of Life discourse, and one possible explanation is that he included it particularly because none of the other gospels did. He wanted to emphasize the Real Presence (though he didn’t include a Last Supper narrative as the others did particularly because the other three contained them).
As for this, just as with anything else, we can only guess. However, Matthew’s inclusion of this event would suggest that including it would help fulfill the themes which he presented.