Heroines are pretty, Villainesses are vain

A standard convention for distinguishing heroes from villains in animation is to make the good characters attractive and the bad characters ugly.  While I am not yet going to discuss the ways this trend is enforced and what it means about standards of beauty, I am going to discuss the irony of this trend in the face of the tendency for villainous characters to be vain.

A classic, obsessed with being the "fairest of them all" to the point of wanting to kill Snow White for being prettier than her.  (Disney's Snow White)

 Not exactly villains, but certainly antagonists.  Typical "most popular girl in school" trope, where their main defining characteristics are their popularity and love of fashion. (Britt and Tiff, My Life as a Teenage Robot)

Villain, for sure.  Her main character arcs involve her feeding off of other peoples' misery to keep herself beautiful. (Spectra, Danny Phantom) - in both episodes focused on her, the way she is defeated is to be 'made ugly'.

The point I want to focus on here is, while heroines are almost universally depicted as being beautiful, they never seem to care about their looks, nor put any effort into them.  Meanwhile, characters who are portrayed as putting effort are almost always villains, where their supposed preoccupation with looks is what makes them so terrible.

However, when villains are not shown to be evil in their quest for beauty, they are (as I mentioned before), frequently drawn to be 'ugly'.  Occasionally, villains are shown to be both vain and unattractive.

So what sort of messages does this send to the target audiences of these cartoons - mostly young children?