I'll take your word for it.
Why doesn't Paul talk about the Eucharist more often? idk. I can only guess. Part of Catholicism is that Catholicism is presupposed in the New Testament, so we believe the Philippians, Colossians, Galatians, Corinthians, and Romans (ecclesial communions) were all celebrating the Eucharist all along and that the institution of the Eucharist was integral and essential to the establishment of a new church community. So the Eucharist was happening whether or not Paul wrote about it, no matter how frequently or rarely he mentioned it. We don't know when the Gospels were written exactly, we know the Gospel of Luke is associated with Paul because when Paul quotes the Lord in 1st Corinthians 11, he uses Luke's phrasing rather than Matthew or Mark's, plus we know Paul and Luke were close.