They also pay him better than any other artist, or so I've heard. To be fair, check out
this link. Yu Yu Hakusho is the tenth best selling Shonen Jump manga ever, Hunter x Hunter is the eighth. On the other hand Bleach is the sixth, so I wouldn't expect it to just be dropped that easily. Also to be fair the hiatuses are reportedly due to Togashi being ill, although I don't think that has ever been confirmed.