1. Bread and wine shows the continuity with Passover.
2. Bread and wine are foods everyone partook of, the basic foods. This breaks down distinctions of culture or class by a common meal.
3. Bread and wine are of more spiritual taste than flesh and blood. Monks, for instance, can't eat meat because not eating meat makes them more spiritually inclined.
4. It shows God is sustaining you, and ties in with "our daily bread". Bread and wine, being the basic staples, are therefore mystically tied to God, the most fundamental of staples.
5. Breaking bread signifies fellowship in ancient times. Food was never a solitary activity. Even drinking water, in the Bible, is always shown to to be a social activity.
6. Proverbs 9:5 (the word here is literally "bread", not food, as in some translations).
7. Christianity is poetic mysticism, not analytic philosophy. Bread and wine as flesh and blood is more poetic and beautiful than raw flesh and blood as empirically observable.
8. Christianity is not only non-materialist, but also generally shuns materialist proofs, since they make faith-without-seeing impossible, and faith-without-seeing is considered childlike and favorable, since it is conducive to a mindset of delight and wonder instead of a clinical one.
9. Without bread, the strong imperative against yeast during Passover in the OT is less meaningful. In Orthodoxy, the Eucharist is always leavened, since leaven is seen as signified the completing, the fulling of the covenant in Christ, adding what was lacked in the Old Covenant.
10. It makes us look like fools and allows us to be derided by those like yourself, which is goodly in God's eyes. If being a Christian made you look intelligent, it would be more likely to draw than arrogant than if Christianity made you look like a fool. "Holy Fool" is even something especially in Orthodoxy, those who are retarded or otherwise "mentally ill," are regarded as gifts from God and to be treated with respect.