I hate to engage in "
politically correct"
deconstruction of a
fairy tale/
legend, simply because it's been done so much. But this one begs it.
In an age when women, especially women of high caste, wer treated as chattel and accessories to political unions, it would simply not do for the daughters of a noble house to refuse suitors simply because they didn't like them. Female mate choice was seen as dangerous, especially since many of the potential mates would be warlike, abusive brutes. Who would choose that? So in this story, the consequence of the seven virgins refusing their societal role is demonstrated - they get turned into rocks. Obviously, their father should have been around to set them straight!
See also uppity women.