As churches grow and expand, many of their basic doctrines are eased to accommodate new groups of people. This is often the reason new sects formed are from their religion, and many of them are looking for what they believe to be closer adherence to the Bible. Religious institutions that allow members leeway in ritual is not the issue; it is the perception that sinning is allowable that causes many people to turn to fundamentalist beliefs when this occurs.
Fundamentalist sects believe the Bible should be followed literally, and there is little forgiveness for those who offer different interpretations. Members generally believe people outside of their church are not true Christians, and they reject any doctrinal differences. They believe there is no compromise from their own views, and this sets them apart from many of the more popular churches in the world today.
Belief in strict adherence to the teachings of the Bible is what sets fundamentalists apart, but it also isolates them from mainstream religions. Most of them prefer it, and their members believe only they will ascend to Heaven. This does not always endear them to other Christians.
Those who practice fundamentalist beliefs are often seen as obnoxious in their faith, but there are many who are truly committed to their beliefs. They try their best to spread their version of Christianity to those around them, and recruiting new believers is one of the more important goals of their church. They do this because of concern for fellow Christians who do not practice the teachings well enough, so it tends to set them far apart from their religious contemporaries.