We need religion because:

(a) We're all scared about the big unknown DEATH.

(b) Our complicated brain chemistry plays all sorts of strange tricks on us.

(c) We're all subject to random events which we can't control.

Long ago some genius realised that he/she could pretend to intercede, on our behalf, with some supernatural being(s)who 'really' controlled these things. This genius could then rake off more than his/her fair share of his/her society's surplus wealth without actually doing very much. Hence 'Organised Religion' was born.