Originally Posted by
Jay R
Each time they start over with a new edition, they are replacing dozens of books with just a few. Some content will not (yet) be included.
Any race that was invented for a specific edition of D&D involves a choice – do we update it to the new edition, or leave it where it is?
By contrast, men (eventually re-named humans), dwarves, elves, and hobbits (eventually re-named halflings) have been in D&D since the first three-pamphlet edition, because players who had never seen D&D wanted to play them.
When you tell somebody about D&D for the first time, after three sentences, nobody says, “I want to play a half-aasimar,” or “Can I be a tiefling?”
But people do say, “I want to play a hobbit like Bilbo,” or “Can I play a dwarf like Gimli?
Races that have, over the decades, pulled people into playing D&D for the first time are more likely to be included than races that people only learned about by playing D&D.
I'm pretty sure that's the real answer. While a lot of content has been invented just for D&D, playing in fantasy worlds like the ones we've read has always been a major draw for a lot of people.