Our most sacred holidays have to do with Jesus, and even the way we speak of the passage of time is a reference to Jesus. It is l996 in the day of our Lord. It is the awesome power and will of the one true God that made this come to pass. There have been throughout history a myriad of religions that cultures have followed. Today there are as many religions as there ever were.
People follow and devote themselves to what religion they consider to be true.
It is not that people do not follow their beliefs, it is that their beliefs are not true. He wants the people of earth to follow. He has preserved these beliefs in the Bible. It doesn't make sense that He would have contradicting beliefs for different parts of the world, because we all live in the same world, and if the beliefs differ, there is conflict. God wants the same values and beliefs for all people and all time.