Relationship to pantheon and cultural origins:
As much as Her a is the idealized noble wife, quick of intellect to be able to run the affairs of the estate smoothly, strong and of regal beauty and firm command (quite different how many imagine Greek women as being oppressed by a highly patriarchal culture, the popularity of Hera certainly suggests otherwise); Leto is the idealized mother, tending to the comfort of the home and the wellbeing of her children with intense mindfulness. To see her presented poetically by the side of Zeus to greet her children lovingly as they arrive suggests a certain prestige of the idealized mother.
Additionally she is the idealized mysterious and exotic nature of woman. She is eroticised when the beauty of her control of what little if herself to be seen…often erotic areas being described such as the ankle or wrist. Here too she is the exotic attractiveness of the foreigner (as in myth she is said to have hailed from Hyperboreia) even if in Greek culture she was both desired but not desirable for a lawful wife (rather like Meadea. ..minus the killing of her children). She is all which is mysterious, hidden and unknowable. ..likely the very way men perceived women in general, and many still do.
She then is a contradiction of perfect mother with exotic mystery woman…the baffling conundrum of mothers.