Baptism is a way to show other people that a person is not afraid to worship God and not afraid for other people to know that. I don't think it is absolutely necessary to be saved, but it does help you feel closer to God in your walk with him.
No one is afraid to worsxhip God since the majority are religious. Maybe people are afraid to be atheists.
The reason is simple, to make reason and truth the enemies of faith. Eating from the tree of knowledge let adam and eve know truth and for knowing truth, god cast them out.
Yeah but why would a supposedly omnibenevolent god who make a perfect world with no bad things create satan who is actually more moral than god who taught adam and eve things which god repayed by ejecting them from the garden. Since god can see the future why would he have made humans since he knew that would happen.