"Nonsense, dear. I've had more visitors than ever seeking the wisdom of the hearth goddesses." Freir

Freir and Rorlund are both Nords and priests of the Temple of the Divines in Solitude. That's the only time I believe the term "Hearth Goddess" has been used. I assume it refers to Mara, Kynareth and Dibella or otherwise two of them including Mara. As priests of the Eight/Nine Divines in the most Imperialised city in Skyrim, their beliefs may reflect Imperial beliefs. As Nords in Skyrim, their beliefs may reflect distinctly Nordic beliefs.

What's noteworthy about those three in Skyrim is that they have their own temples. Aside from Talos, Arkay and the Vigilants of Stendarr's base, the other gods do not. They are also closer to their traditional Nordic counterparts than the others. Another thing that sets them apart from Shor and Tsun is that they didn't die in Nordic myth.

My own speculations are as follows:

• The goddesses are actively worshipped because they're alive. The Nords see no point in praying to dead gods and may not expect such prayer to even be heard although those who know the stories respect their deeds. The dead gods are more relevant once the Nord enters Sovngarde. This is partly based on Vilkas' comment on Talos being dead and thus irrelevant and I doubt the former point is common amongst the faithful.
• Officially, the goddesses usually have the same formal and impersonal relationships with Nords as desribed in Reflections on Cult Worship. This is in contrast with Talos who loves his followers as individuals because he was once man and so is closer to them, much like the Living Gods and recent ancestors of Morrowind. In practice, some Nords may assume that the same type of relationship applies for other gods, particularly the goddess of love.
• The goddesses are considered the part of the pantheon that cares for and nurtures mortals most readily. As such, Nords turn to them first in moments of weakness when they need help. In other mannish provinces, Stendarr has this role, but the god of mercy as opposed to the god of the ransom is relatively new to Skyrim, so his niche was already filled by the hearth goddesses.
• The hearth goddesses gained popularity in High Rock when it was mostly under Nordic rule. Kyne was worshipped in Nordic settlements including Daggerfall, Alcaire and in the Wrothgarian Mountains which were more hospitable to them than the natives. Her popularity with Nordic warriors in particular often presented her as an enemy to natives. Dibella appealed to Bretons in the lands outside Alcaire, possibly because a goddess of their own (like Druagaa, goddess of flowers) was interpreted to be the same as her, unlike Kyne. Mara was the most widely adopted of all, especially in the west, because of the ubiquitous acknowledgement of mother goddesses and the cult's tolerant and compromising ethos, both of which would protect it from Aldmeri persecution. This is based on the arbitrary temple distribution pattern in Daggerfall.

Please share your ideas, unless they're "11/11/11. They only had time for five gods.".

Would they be much like the Tribunal since Lorkhan's heart made a good example of what gods of the flesh would be like ? or is your speculation meaning that the goddesses are similar to the daedric princes?

People in Tamriel in pray to the divines and expect some responses. What I'm suggesting is that Nords don't traditionally pray to Shor, Tsun etc. because they don't believe those gods can answer their prayers because they were killed and are no longer in their world. Whereas if they pray to Kyne or one of the other goddesses, she will hear it and may answer.