Pure and simple, King’s more important.
We‘ve already seen two other characters from MADS and Vegapunks’s the really important one, so Queen isn’t exactly special because of him being a member.
And Oda just doesn’t give a fuck about Jack anymore.
Whereas King’s Kaido’s right hand, and as the only living member of his race (that we know of) he’s going to be the main face of this obviously important Void Century plotline of the Lunarians.