I think it has a relation to sociological context, influencing behavior and appearance.
(Most) Animals and birds don't know things called 'status' and 'certanties'. So in case of animals, the male is more dependant on his appearance, through which he wants to show his better genes towards the female. He must appear better.
In human society, females were historically more dependant towards a man, who could take care of them, and moreof: their children.
So, to be able to attract the propre man, with the status and resources to do all that, they must be able to seduce him. To be able to do that, they always must take care of having the good looks, to strike when 'the rught one' crosses their path.
It's nothing more than a practical matter expressed through evolution.