John's Gospel and the Last Supper

Q - Why do scholars suppose that John left the blessing of bread and wine out of his Gospel?

A - Thanks for the question!

The most popular answers, and probably the best, give us two reasons:

1. John wrote his gospel after the other three Gospel writers wrote their's as well as St. Paul's account in 1 Corinthians. So, the Church already had their accounts and he wanted to emphasize something different in his Gospel - the washing of the apostles' feet.
2. John had already given us the discourse on the Bread of Life (John 6) which is the fundamental teaching on the Eucharist in his Gospel. Therefore, there wasn't as much of a "need" for John to give an account of the Last Supper as the synoptic writers gave us. But, he gives us the longest account of what Jesus taught at the Last supper (chs. 13-17).
   

Remember that the early Church already struggled with community problems, as St. Paul writes about in 1 Corinthians 10-11. So, John was emphasizing that Jesus not only preached it, but lived it and that He calls us to do the same. The Eucharist is meant to change us outwardly, not just inwardly.