Have you ever noticed that almost all of our prayers are in the plural? We address God in the Amidah as "our God and God of our ancestors." During the Days of Awe we refer to God as "Avinu Malkenu," "our Father, our King." On Yom Kippur we ask God for forgiveness "for the sin which we have sinned against You." And so on and so forth.
Which makes it all the more interesting to note that the Ten Commandments are all in the singular. You may not notice this when reading an English translation since "you" in standard English is both singular and plural. (There are of course dialects which do distinguish between second person singular "you" and second person plural such as the Southern "y'all" or the New Jersey/Philadelphia "youse.") But when God says "I am Adonai your God, who brought you out of the Land of Egypt" or says "you shall not kill" or "you shall not steal," the Hebrew is in the singular. It is not a collectivity being addressed, it is an individual.
Rabbi Ismar Schorsch, Chancellor Emeritus of the Jewish Theological Seminary, says that Judaism in general, and Conservative Judaism in particular, is about "balancing the polarities." Is Judaism concerned with the needs of the Jews or the needs of all people? The answer is both. Is Judaism concerned with the spiritual or the material? The answer is both. Is Judaism concerned with perfecting the individual or creating the beloved community? The answer is both.
We stray from the right path when we focus too much on one pole and lose sight of the other. If we are not concerned about the needs of Jews, we will not survive as a people. But if we are only concerned about the needs of Jews, we have no real reason to survive as a people. If we are not concerned with spirituality, our souls will starve. But if we are only concerned about spirituality, our bodies will starve.
Our liturgy is in the plural to remind us that we are a community, a collective, that we are responsible for each other. Perhaps the Ten Commandments are in the singular to remind us that each of us, individually, has our own relationship with God; and that each of us has a responsibility to fulfill the covenant, and not depend on others to do so on our behalf.