There have been efforts to unite the mainline churches but none have been successful. There are simply too many differences, most in the way of customs, traditions and beliefs that separate the churches. We live in an age when denominational ties are not as sacred as they once were.
People tend to switch from one faith to another with little difficulty.
In the past most of our church folks were born into the church. Now folks actually go church shopping. They tend to settle in a church that most closely resembles their own understandings, meets their comfort level or fits their life style. When I look at my own background I soon discover that my faith experience is a hybrid one. In my family there have been Methodists, Baptists, even native American Indians.