In June 1961, DC published a super-collection of many superhero origin stories entitled Secret Origins, a one-shot. I’m a sucker for origin stories and I really liked the 1986+ series of the same name, which helped solidify DC’s continuity in a post-Crisis on Infinite Earths timeline.
But back in the 1960s, there was no really good way for kids to learn the origins of some of the characters. No internet, no collected works at the library, etc. So I bet it was really good advertising!