Drunks and junkies are alive when they have those hallucinations. I think its unfair to compare them to a person who is temporarily dead until they are medically revived via CPR or other methods.<quoted text>
For the exact same reason that lots of drunks see pink elephants and junkies see, and feel, bugs inside their skin. Same reason people think little green men sexually molest them. It's cultural iconography, what you see, or want to see, most often is what you are more likely to see when hallucinating.
A better question is, if there was more to NDEs, why is it that every single religious belief produces vastly different NDEs?
'...why is it that every single religious belief produces vastly different NDEs?'
It might be that God lets souls experience the after-life in a way that won't make them doubt their religion when they re-enter their bodies. For example, if a Muslim dies and experiences a Christian Heaven and then returns to his body, he probably wouldn't want to tell his fellow Muslims that Heaven is a Christian Heaven. If he does, he might be beaten up and/or killed.