For me, having an encyclopedia at home was a huge help with my studies and even finding out what I wanted to do/be later in life. This was 40+ years ago and I also had or had access to a lot of other books but never found them disappointing at all.
I now like the fact that they, as books, are frozen in time. And that their knowledge is well packaged and consistent. Unless you're a researcher, you don't need the latest. And as a child, the clear writings and the great illustrations was key to internalize the knowledge.