With so many positive messages in all forms of scripture, is there a solid argument why people should not spend time learning about many types of religion, regardless of their beliefs?

I’m not religious, but I’m not an atheist. I fit pretty well into the agnostic category I suppose. I often read sections of scripture though, because I agree with the uplifting and positive nature of most of it. I’ve read different versions of the Bible, sections of the Koran and excerpts from the Torah. With all of the positivity throughout these various books, why are people so against reading anything other than their own version? Wouldn’t we be better off if we read and understood many of them?