Well, title may be silly, what I mean is, during Daedric quests, deadric princes communicating with player. Especially in Oblivion if you touch the shrine they're answering, you all already knew that. But why Aedra is not talking with us? Is it because of Imperial Covenant? Or they just do not care about mortals?

Because they're dead.

You mean, truly dead? So there is no Aedra and their planets actually their corpses? Then how Martin Septim called Akatosh? Was it fake?

Well, the only god that's really truly "dead-as-a-doorknob" dead is Lorkhan. Only Lorkhan's ghost (the Shezarrine) remains.

The Aedra are still kinda alive; they're only dead in the divine sense - i.e. they are no longer eternal.

At least, that's my knowledge of it. It's probably a little more nuanced than that.

I'd say not so much dead as in a coma, only sporadically reaching brief moments of wilfulness and agency when the faith of mortals is strong and focused enough to stir them from their slumber.

There's lots of stories from varying creation myths that attempt to explain what has become of the Eight (+1) Divines, but what I believe roughly happened to them was that the Aedra involved in creating the Mundus had to sacrifice their power and sentience to provide the fledgling mortal realm with the energy and stability it required to flourish. They became the Earthbones, the foundation upon which the material plane was formed. Not only were they bound to the Mundus, but they became a part of it and it is very difficult for them to break away from that binding slumber. They are only able to achieve it when mortals offer exceptional prayers or sacrifices (like Martin Septim giving up his life to allow an avatar of Akatosh to materialise on Nirn).