Goblins should be in the 5.5e or 6e PHB, clearly.
If they're being reprinted that many times, they're really a core player race to too many settings to push off to splatbooks.
I'm wondering how many of these reprints are because Wildmount grew out of Critical Role games that would have played through the various splatbooks of 5e and players would have been like, "oo! shiny new race in this book!!"
Also, this is GREAT news for Core+1 games. I'm guessing they only got away with it because Wildmount in all likelyhood will NOT be AL-legal…