The voice that is heard is authoritative. Now Buddha story sound like he is reponding to a voice that is authoritative. Although most suttas makes us have the impression that they are just myth. They are still teaching there is this voice coming from high. And people that hear it hears it louder than a person standing next you.
We need to understand Brahma was believed to be the authoritative voice coming from high and as long as you are in the world your connected to it. But there is no reason to reject it also.
(Reason it might not have been called Maha-Brahma in all traditions is because they dispute probably what that authoritative voice is)
Brahma Sahampati:
It is not in such a way that the Tathagatas are to be venerated, lord of the devas. The Tathagatas are to be venerated thus
https://suttacentral.net/sn11.17/en/bodhi?reference=none&highlight=false
For the one come to peace in himself
there is not the assumed, from where the rejected.-Buddha(TUVAṬAKA)
There are many individual Brahmas with names presented in SN Brahma Samyutta (and its Chinese SA versions). Brahma Sahampati is not Maha Brahma.
Hello again. Not my point. It doesn’t matter. You see him showing more authority.
I said not every school chose to use that name. In Mahavastu for example used mahabrahma. The idea of Brahma Sahampati is obviously the name chosen by those that didn’t want to use Mahabrahma. But my point is that people experience hearing a loud voice. From there the ideas of these myths. In time of Buddha they probably hear better.
The authority is the Buddha, not the Brahma/s, indicated in the Buddhist texts. Also, many Brahmas, not just one Brahma, are the early Buddhist adaptation-style in response to the Vedic religious notion of Brahma.
Reply if interested to understand my post. These are serious topics for those interested.
Chosen by who? I think it is chosen by early Buddhists shown in the texts.
Remember my title is not if he is Maha Brahma or not. My point is many experience very loud voice and it’s authoritative. So it’s something this world has because the Brahma net let’s assume. The part I say that Brahma Sahampati looks authoritative is because he replied correcting Sakka. For me it doesn’t matter what name they chose but there is one voice. Each deva in suttas is those voices in us but it can sound very loud.
What is “very loud voice”?
Both Brahma Sahampati and Sakka respect the Buddha and his dharma/dhamma very much.
I think, the very loud voice of “anicca-dukkha-anatta” is the one voice for both each deva and all of us.
I don’t think that without a reason Pali Canon has that the Brahma at DN start in heaven. We are really in Brahma net. It’s not a myth. That’s why this voice say acts like a father of you. Say things like because you forgot your father. In manly voice. For me this voice was probably what created all the myth looking Brahma talking not do things. Because the voice acts authoritative. But the point of Buddhism is not see it as superior. Because litterly it makes you feel that way. Just because it sounds coming from high.
This was the matter of Brahma Sanaṅkumāra’s speech. And he spoke it with a voice of eightfold characteristics—in a voice that was fluent, intelligible, sweet, audible, continuous, distinct, deep, and resonant. And whereas, lord, Brahma Sanaṅkumāra communicated with that assembly by his voice, the sound thereof did not penetrate beyond the assembly. He whose voice has these eight characteristics is said to be Brahma-voiced.
Exactly the voice that they call Brahma voice @thomaslaw
https://suttacentral.net/dn18/en/tw_rhysdavids?reference=none&highlight=false
The voice sounds loud but it doesn’t seem to go further than you.
The Brahma Sanaṅkumāra’s voice is in fact his speech, which follows the path of the Buddha.
Again. You always do this. Are you send to just keep replying like this. 
seem a robot against troll. But I’m being serious always and you come. Anyways like always bunch replies with no asking what I mean. For example I meant look how the suttas made a myth story. Decribing the quality of a Brahma voice because they probably where familiar that the voice sounds deep. Audible. Exactly how nowadays people decribe it. For me it’s no a big deal. There is small voice already in our head. But this one can truly then teach Dharma let’s say.
I’m aware of this
He perceives the heard as the heard. Having perceived the heard as the heard, he conceives himself as the heard, he conceives himself in the heard, he conceives himself apart from the heard, he conceives the heard to be ‘mine,’ he delights in the heard. Why is that? Because he has not fully understood it, I say.
But no need to reject your inner voice. But is there a outer voice also?
Buddha itself believed duality projected out of humans that sun and moon etc was created. So if inner voice was something inside humans did it project out to the world? 
Obviously we can’t tell. But Buddha point is the world is a projection of our inner conflicts. So maybe we always had conflict with following our inner guidance that it projected outside. It’s mainly because our ancestors. The first teachers of humans. Like any ancestral custom mostly it becomes a universal net
