Of all of the things the Lord could have commanded us to do in remembrance of Him, He chose the institution of the sacrament. We are specifically asked to remember His"body," and His "blood, which was shed for [us], that [we] may always have His Spirit to be with [us]."
Jesus could have asked us to remember His example, His healings, his Sermon on the Mount, or any particular teachings. Perhaps one reason He asks us to remember his body and blood is because He wants us to always be reminded of His love for us. His kindness, patience, and compassion in spite of His own infinite pain and suffering are proof of His infinite and enduring love for each of His children.