I mean I think that the reasons are just as varied as people themselves. I think a lot of times it’s tradition in the sense that their parents believed it, there parent’s parents believed in it. So, it’s easy to just do what everyone else does.

Then you have, especially in Islamic countries a situation where their religion is everything. From the government, to the judicial system, to the education system, and of course the religion. It’s a way to control to masses. I think it was Hitler that said “He alone that owns the youth gains the future”. Indoctrinate your people early and reinforce it every step of the way.

Then you also have a situation where Muslims pray multiple times a day. Once again this just reinforces the indoctrination, but it also serves as a constant reminder that if you “sin” bad things will happen.

All of these things and more help to cement a tight grip on a population. There is a YouTube channel hosted by an ex-Muslim that I find interesting. The dude is way smarter than I. The channel is called “Apostate Aladdin”. He does a great job of explaining things in easy to digest ways.