To be fair, The Hobbit didn’t start as a Middle-earth story and was retconned into being one after he started writing the sequel. Which is why the only mention of Hobbits in The Silmarillion is a line at the very end about Frodo destroying the One Ring even though The Shire either was a client state of Numenor before it sank or is the last remaining part of the Numenorean government.