Pastor Bruce Timm wrote a series on Why do I use the Liturgy? which are listed here. The first three parts were produced as one article, so they link to the same article.
Reason 1: The liturgy rescues from the tyranny of the old Adam.
Reason 2: The liturgy rescues from the tyranny of individualism.
Reason 3: The liturgy rescues from the tyranny of contemporary culture.
Reason 4: They used the Liturgy in the Garden of Eden
Reason 5: The liturgy teaches the young and sustains the old.