If you are a Christian, are all Muslims sinners? If you are Islam, are all Christians kafirs? Hindus are more accomodating.

Religion is a major feature of human civilization. It is on the same rank as fire.

Religion is so entrenched in our civilization that we all adhere to it. As an individual, you must relate to another individual as a religious human being.

You are Christian, Muslim, Hindu, Athiest, Rastafari, or any other religion. Religion is such a prime pillar that Robert Green included religion in his infamous 48 Laws of Power.

48 Laws of Power | Law 27: Play on People’s Need to Believe to Create a Cultlike Following

This will come out as offensive to some of you, and If it makes you feel it's real. Honestly speaking, in a way other people will not judge you, why do you follow your current religion?

These are your reasons:
1) Your parents were introduced to the religion.
2) You follow the most common religion in your society.
3) You have researched, investigated, and made a conclusion to follow your current religion.
4) You are faking your religion for some other reason.

If your reason is on the list, let's go deeper. Among the known human civilizations, there are three types of religions. 
1)Monotheic religions(belief in one God)e.g Christianity an Islam.
2)Animism, belief in innumerable spiritual beings concerned with human affairs and capable of helping or harming human interests, e.g. water sprites, vegetation deities, and tree spirits.
3)Polytheism, the belief in or worship of more than one god; e.g. Hindu.

My question is, "Why do all human beings conform to these 3 types of religions?". Please, only read this if you are ready to be insulted. Things you'll read are either things you agree with or disagree with or things that insult your current beliefs.

POINT 1:
Monotheistic religions
This is the foundation of all religions. Christians believe in A God who is a spirit. Muslims believe in Allah who is also a Spirit. Other religions too. A spirit is something occupying space.

We all started here. But as our civilizations advanced, we needed something more unifying than 'just a spirit'. At first, it started as spirits we all understood. Some of these spirits were the sun, and the moon among other spirits. Abraham who is in all religions started here. He was a star worshipper before both Isaac and Ishmael.

The rest will be discussed in an X(twitter) space. The link coming soon.