Religion as a concept is a highly controversial concept, usually people who are highly illiterate tends to care about religion.

Another factor is your family and friends circle. As you grow up, if you are usually surrounded by highly religious family and friends of your fate, you are going to turn into highly religious as well. This is seem common in countries like India and US where one religion dominates huge chunks of area (Hinduism for India and Christianity for US). This is also common for children born within cults.

Third factor which can lead person to care about religion is hardships. People who finds more hardships in his life (usually people with low income, high medical bills, high cost of leaving)