I think the issue is that when it comes to novels, the visual elements are not shown, so reader`s imagination fill the blanks.
You may have a really cool and sexy design in your mind for your dragonshifters, but conveying that is trickier. Werewolves and vampires have an established presence in pop culture and media, so the mental image on how they can be attractive is already there.
I am not saying that dragon shifters can`t be pretty, but on novels is way trickier to convey the visuals the way you expect.
edit:(just to clarify, i mean the humanoid form)