Churches are peaceful, and have a serene atmosphere. This gives your wedding ceremony a special feeling and makes it an experience, an occasion. It adds a spiritual dimension to your marriage and recognises that there is more to life and marriage than just us.
Also, if you get married in church, you can invite as many people as you want to the service, to see you actually getting married. You are not restricted to how many people you are inviting, as perhaps in other venues like a registry office or an hotel. Therefore a church wedding is more inclusive.