Since Disney more than any other studio has a toy line of dolls (like Matel does with Barbie) and they only care about profit this makes sense. Whatever face sells the best in toyland wins and will be replicated as female dolls and film to make max $$ not the male dolls. Also if they all look like a similar style the…

There are tons of different women in frozen of all shapes and sizes if you watch it again but they aren't the main hero or villian as it wasn't Big Hero / Princess 6.