What makes people irrational thinkers?

[Belacqua]

I always doubted my own beliefs and it led me to atheism and rationality on its own.

At this point, do you still doubt your own beliefs? Have you continued to question what you hold to be true? Or do you feel that now you've arrived at atheism and rationalism you've arrived at the destination?

Why is it some people even from a young age just refuse to think for themselves? 

I want to be sure that when we use the phrase "refuse to think for themselves" we're not just using it as a synonym for "refuse to agree with me." A lot of people think for themselves and reach different conclusions. 

As for why people stop questioning, I suppose it's common for people to find a kind of web or system of ideas which they find sufficient. It seems to describe the world as they see it. If they hear about something that doesn't fit with their system, they can just declare that it wasn't reported correctly, or their preferred system will get around to explaining it eventually, something like that.