I’ve never read Norton, which is odd, her being one of the most celebrated science fiction authors of her generation. But I think it’s like this: I started reading SF at a time when Norton was still a relatively new author. By “relatively new,” I mean her books began being published around the time I was born, and I began reading SF at age 8. When I did, I started with Bradbury, Williamson, Clarke and Blish, segued to Asimov and then to Heinlein.
All of these authors, while around the same age as Norton, were published in book format long before she was. Heinlein wrote juveniles beginning in 1948, Asimov published Foundation in 1951, Bradbury published The Martian Chronicles in 1950. Norton was writing in the 1940s, but her work was predominantly featured in magazines. I didn’t have access to SF magazines as a kid. What I had was the school library at a small, private school. The SF collection was more likely to be the tried and true novels of ten years ago than anything up to date.