Hussar
Legend
The only reason they "aren't in" Greyhawk is because they didn't exist when Greyhawk was originally published.
/snip
BINGO!
Once upon a time, there were really only two settings for D&D - Greyhawk and The Known World. Now, The Known World was only for Basic/Expert D&D, and it was kept very separate from Greyhawk. But, anything else that was published for D&D was published FOR Greyhawk. Anything not set in the Known World, published before 1987, was meant to be set somewhere in Greyhawk. Pretty much anyway.
So, the notion that Greyhawk isn't a kitchen sink setting ignores pretty much the first 15 years or so of the game's history.