Why does GOD do this?

To each their own. Some people actually believe in a higher being, God, and that he controls all aspects of life, including when someone dies. Just because you don't, doesn't make someone else weak. Like you said, upbringing plays a major part in life, and if someone was brought up to think God has a master plan for everyone, then why would that make their thoughts a form of denial?

I'm impartial on the subject, mainly because I need first hand evidence to believe in certain things, but I'm not going to call someone else weak or in denial because their beliefs are different than mine.