When reconstructing ancient Egyptian religion, one must consider the position of a Nisut or King.
First, what was the King?
In ancient Egypt, the King was the political leader of the nation;
it was believed that the ruler had two bodies; one
was the human form.
The second part of the King was the spiritual emanation or kingly ka of Heru (Horus).
In Kemet, one wasn't a King, one became
the King. This was done through the coronation ceremony.
The office of the Nisut was divine, and through this office -- granted through the coronation ceremony -- the person
in the position
was believed to have the
kingly ka of the Netjer Heru.
The gender
of the King didn't matter; the King's divine Ka was always masculine. The
vessel (or body) of the Kingly Ka could be male or female.
Here are reasons to have a Nisut:
Historical Precedence
Throughout the majority Kemetic history, there was an institution of kingship.
High Priest
One of the other duties of the Nisut was to be the symbolic spiritual leader
of Kemet. He was the Priest of the Kemetic religion. Since the King
can't be everywhere at once, He appointed other priests to do the
rituals for Him at all the other temples. The King also performed
the rituals.
Intermediary
Another role for the Nisut was to be the intermediary between
the Gods (Netjeru) and Humanity or the Seen and Unseen worlds.
While the religious reasons above have been reasons I have heard for some
modern Kemetic organizations to have a Nisut,
I have also heard of reasons not to.
Here are reasons I have seen for not having a Nisut:
Historical Precedence
Yes, there were times when Ancient Egypt did not have Kings.
A Nisut was not in place during the Pre-Dynastic Era, and after the Roman conquest.
Chieftains during the Pre Dynastic Era had the title Heru (which is a title of the King in later periods).
After the Romans conquered Egypt, there was no Nisut, but the religion did survive until the sixth century
of the Common Era, when the Temple of Philae was closed by the Emperor of Rome.
More than one Nisut
Also when there was strife
in some periods of ancient Egyptian history, there were two Nisuts governing their own territory in Egypt.
Priesthood
Priests were appointed by the King to carry out the daily ritual and temple functions of the deities.
They did the rituals in the name of the King. They are identified with Heru during the rituals.
There were also councils of priests in each of the temples to make decisions.
Some believe that this would also mean that the priests would also contain the Kingly Ka for
the duration of that ritual which would negate the need for a king.
Location
We are not in Egypt, we do not have a nation and the role of the King as the monarch is not needed.
Intermediary
I've heard people say there is no need for an intermediary between humans and the Netjeru.
This could come from people who don't want hierarchies in their faith to people who are concerned
with giving any one person that position due to its potential of abuse of power.
Personal Piety
People who were not priests did offer to the deities in Ancient Egypt. Home altars have also been found.
This could be an addition to not needing an intermediary arguement.
However one views this issue it would involve trusting the person holding this position to do this duty well -- with
integrity, maintaining a healthy community dynamic and the blessings of the Gods.