What makes you think that molecules 'need' to exist; as opposed to just existing ?
Scientists start with the assumption that there is no purpose to life and that material things can 'just exist'. Therein starts the purely material philosophy of science.
Other people start by thinking that nothing can exist without a purpose and therefore they try to find a meaning and purpose to life in the world.
Both are valid assumptions to begin with.....but what do we observe?
We observe that life has taken a very complex and sophisticated path leading to humans. In addition to that, we have eminent physicists supporting the idea of Consciousness being fundamental in the universe. We also have phenomena like NDE's and reincarnation events (in the OP). What does all this show? It clearly supports the second assumption of there being something more than chance driven material existence.
This should be clear enough for everyone...but no...not for science enthusiasts!
So...what do they do? They dig in their heels and start arguing that there
need not be any answer to the 'Why' question. NDE's are
hallucinations. Reincarnation incidents are
rubbish and made up. Things can '
just exist'. Evolution of complexity is entirely due to
random variations and chance environmental factors....and so on and so forth!