Half-a-dozen facts:
1.
The Hobbit was first published in the U. S. in late Feb. 1938. By the end of 1938 it had sold more than 5,000 copies.
2. Paper rationing began in England in April 1940 and ended in 1949.
3. Allen & Unwin's warehouse in north London was bombed in 1940, and more than a million books were lost. Whoa.
4.
The Hobbit was unavailable in England for long stretches in the 1940s.
5. A reviewer (Marcus S. Crouch) wrote in 1950: "
The Hobbit had a mixed reception, as of most books of marked originality. It has been, I believe, no more than a moderate success in the bookshops, and librarians who have had the courage to buy it in suitable quantities cannot claim that it rivals the popularity of current mass-produced goods."
6. Sales of
The Hobbit picked-up dramatically after the publication of
The Lord of the Rings.
Thus, for the first 15 or so years of its existence,
The Hobbit was not a very popular book. It wasn't a Harry Potter or a Twilight. It was one of those books you see on a bookstore shelf that you've never heard of, written by someone you've also never heard of.
The Hobbit began to be read avidly precisely as a prelude to
The Lord of the Rings. No wonder
The Lord of the Rings has sold more copies than has
The Hobbit. There must be quite a number of people who have read
The Lord of the Rings without reading
The Hobbit. Perhaps these people have little interest in a children's story, but like the more adult-oriented
The Lord of the Rings. Perhaps they feel that the four-page summary of
The Hobbit in the prologue of
The Lord of the Rings is all they desire to know about
The Hobbit.