I agree the white text is a bad choice. Why? Because it is "aggressive" it is "in your face". It screams because of its high contrast. It distracts you from the content you are supposed to be reading. It makes you think you are in a black-room looking at some negatives. Perhaps some secret content.
When you read you should be able to forget that you are reading, your mind just "drops in to the story". That happens with books with black text on white background. You read but you are unaware that you are reading. Your mind just consumes the content.
Maybe part of it is convention since we are used to books and newspapers and magazines not having white text on black background. But I think there's more to it. Black background is like paint, whereas white background is lack of paint. There is no background there is only the text. There is only the content. Therefore you can more easily forget about everything else and focus on the content, on the message.
When you read you should be able to forget that you are reading, your mind just "drops in to the story". That happens with books with black text on white background. You read but you are unaware that you are reading. Your mind just consumes the content.
Maybe part of it is convention since we are used to books and newspapers and magazines not having white text on black background. But I think there's more to it. Black background is like paint, whereas white background is lack of paint. There is no background there is only the text. There is only the content. Therefore you can more easily forget about everything else and focus on the content, on the message.