I know this makes me seem slow, but I have always wondered why weird religions are the only people to use such art. It is very unique to religions, this pseudo realistic, historical oil painting Style.
The answer is so dumb and so obvious..... There is zero evidence, there is zero to show. They can't talk of able dying and show a picture of Eden, or a grave site or a physical remain from Adam and Eve's belongings. when you have NO evidence, you either have no pictures or you paint them. They have no areas,no items, no remains, nothing..... Just some stories on some scrolls. The weird paintings are not optional, it's all they have.
Open up a textbook,see what pictures are used.
Ironically I can only think of one other genre that uses such pictures.......fairy tales and stories for children.