I buy them and use them.  Usually from DAZ (pre-Genesis) or RDNA. 

To be blunt, the thing that makes them most attractive to me is low price.  They tend not to be used that much, since they are so distinctive looking. Even different textures don't really fix that.  So typically I will not spend a lot on monsters.

Dinoraul's dinosaurs are an exception, but I don't know if they count.  (I would love more textures for those.  Especially feathery ones.)

As for something that hasn't been made...I would like some alien steeds.  Fantasy or SF horse-type creatures with saddle and tack.