Why couldn't Paul point back to Matthew's Gospel for the Lord's Supper account?
Paul could not point back to Matthew’s Gospel because the Gospels had not yet been written. Before those accounts existed, Paul wrote to the Corinthians the same words concerning the Lord’s Supper by revelation, showing God’s order. So the account came to him directly, not from an existing Gospel record.
Les explains that this was probably the first time Jesus is quoted chronologically in the Scriptures, because the Gospels had not yet been written. Paul therefore could not delve back to Matthew or one of the other writers and say this came by revelation from an existing Gospel account. Instead, before the Gospels were ever written, Paul wrote the very same words to the Corinthians. The doctrinal reason for the Lord’s Supper is that as often as believers eat the bread and drink the cup, they show forth the Lord’s death. Les also notes there is no stipulation from the Apostle as to how often a church practices the Lord’s Supper.