Why do you think the doctrine of separation between church and state is a continuing issue?

Back in the Roman empire and renaissance ages the church was essentially known as the "power house" of the government. They may have had an emperor or king or queen, but the church was always controlling things. Many people started to break away from the churches rules/laws when Martin Luther (not Martin Luther King) came along. He basically exposed the church and how they shouldn't be charging fees to "forgive" peoples sins. Now days the church is not in anyway shape or form in control of MOST governments. Though there usually are some conflict over laws, the church does not have nearly as much power in government as it used to.