When my family moved to St. Louis in my teens, we went “church shopping”. It’s probably the only time that I’ve done this since I was relatively unchurched for much of college and then I was assigned my churches from that point on without much choice in the matter. I remember that we would go to a church, and then on the ride home or at lunch we would talk about the pros and cons of different churches. I remember that my brother and I had a strong distrust of what we called “organized churches.” 
This didn’t mean that we were skeptical of organized religion. It also didn’t mean that we were skeptical of liturgical churches. It meant that we were skeptical of churches where the ushers would dismiss the people row-by-row, starting at the front and then working their way to the back. This wasn’t even a timing thing for us, we usually sat up front and were some of the first to leave, it just felt weird for it to be so….well…organized.
So I understand when people who haven’t grown up in a liturgical church ask the question, “why does your church follow a pattern?” To them it seems overly formal, like being let out of church row by row instead of everyone mingling together after worship. But when you understand the pattern, maybe it’s a little more understandable. Hopefully it’s at least a little more understandable than being ushered out row by row, which I still don’t really understand.
The liturgy is a pattern. This is what most folks think of when they are asking why we follow a pattern. The pattern is actually meant to move us from our Baptisms (invocation) to our sins (confession) to a state of forgiveness (absolution) which leads us to praise (hymn of praise) to a quieting of the soul to hear God’s Word (the readings/sermon) to a faithful response (prayers, offering, confession of the creed) to finally receiving God Himself (Baptism/communion), to being sent with God’s blessing (Simeon’s song, benediction). We follow this pattern because it rehearses a story of salvation for us, and in some ways, shows us the pattern of God’s work in our lives – birth to death.
Additionally, our Bible readings and sermons follow the pattern of this thing called “the lectionary”. The lectionary is a collection of three years of four readings per Sunday (plus a few other special days). The point of the lectionary pattern is to keep things fresh and well rounded. Churches that don’t use a lectionary or a system of readings are more likely to hit upon “hobby horses” or things that get preached about over and over again. For example, I had a friend who said he grew up in a church where the pastor preached about Genesis and Revelation, and really little else.
But to be honest, I’ve never been to church service where I didn’t see a pattern at work. I suppose there is someplace where nobody has planned any part of the worship service, and so it’s all off the cuff and possibly randomized, I just haven’t seen that. The closest I’ve seen is a Lutheran church that purposefully mixed up the normal order of events as a sort of “anti-pattern” which was honestly more frustrating than freeing.
Sometimes patterns and organization are a little too much (i.e. the aforementioned “organized churches”), but most of the time, patterns and organization help us to follow along and pay attention to the important stuff rather than the lack of pattern. There’s beauty in both the pattern and the breaking out of pattern. To fall in love with either pattern or its antithesis is idolatry, but each can be helpful, even if they are a little…well…organized.