Tribal leaders were included as an after thought in the Constitution. Their inclusion was a purely political decision which was not justified by any legal or governance principles. It is amazing how similar pre-Christianity religions and pre democracy governments are for a variety of people scattered around the globe. Government by hereditary chiefs seems to have been universal at some stage of human development. An extension of this system was a hierarchy of "nobility" from the chief and his relatives to certain "important" families of aBanumzana who, together with the royals, constituted the higher class of aristocrats.
In Southern Africa the population density was relatively low at the time when colonialism began because although the Bantu people were farmers agricultural productivity was low compared to Eurasia because the only energy source was human muscle whereas in Eurasia and North Africa Agriculture was powered by animal muscle. Our feudal system was therefore relatively benign because land was plentiful and commoners were not exactly serfs.
Though commoners were sometimes expected to work in the royal agricultural fields, this labour contribution could be considered as payment of tax because the Chief had to be remunerated for working as the Chief Justice and President of his people. The rest of the noble hierarchy acted as the lower courts and administrators of regions and villages depending on seniority. However the system of governance was as undemocratic as the justice system was largely unjust.
For the benefit of those who might be thinking that the preceding paragraph refers exclusively to Africa, consider the following passage from Adam Smith's "Wealth of Nations" in which he describes judicial authority in feudal Europe:
The judicial authority of such a sovereign, however, far from being a cause of expense, was for a long time a source of revenue for him. The persons who applied to him for it were always prepared to pay for justice, and a present never failed to accompany a petition. After the authority of the sovereign too was thoroughly established, the person found guilty, over and above the satisfaction which he was obliged to make to the party, was likewise forced to pay an amercement to the sovereign. He had given trouble, he had disturbed, he had broke the peace of his lord the King, and for those offences an amercement was thought due.
In colonial Africa chiefs came under the direct control of white magistrates and their judicial authority was reduced to adjudicating minor tribal and civil disputes in terms of customary law. Their administrative responsibility mainly consisted of allocating plots in tribal communal lands. The Chiefs got small salaries from the colonial government which they supplemented by getting people to (pay an amercement or "cold drink") i.e. bribe them for any of the services they provided in rural villages.
The formal judicial system largely deferred to chiefs on matters relating to tribal law which had a much higher status during the apartheid and during the colonial era. However, the 1996 constitution takes precedence over all laws and therefore only those tribal laws which are consistent with the constitution are valid today. The problem is that tribal law is largely unwritten, which suits unscrupulous chiefs just fine, and there have been few opportunities to test them against the constitution given the high expense of litigation.
Given the fact that tribal law has now been subsumed by the constitution there is no longer any matter which is under the exclusive jurisdiction of tribal law. All litigation can be handled by magistrates. Furthermore the administrative duties which were once the exclusive preserve of chiefs are now supposed to be handled by local government. The sources of extra revenue for the chiefs have dried up which is why they are almost always at loggerheads with the local government councils.
The ANC has always considered the traditional leaders as the key to the tribal vote.
What is the role of chiefs? Today the chiefs are little more than titular heads of local government. In the case of KZN there is only one king in the province which makes him titular head of the provincial government. This has caused a lot of complications for the government because other tribes and provinces have multiple kings but that is another story. One of the few matters that are under their jurisdiction are tribal customs such as initiation. The practice of that custom is a mess with circumcisions being botched and initiates killed or maimed.
The context is that the ANC has a long history of collaborating with tribal leaders. In fact during the founding conference of the ANC in 1912 all the senior tribal leaders in South Africa and surrounding countries were invited. The ANC has always considered the traditional leaders as the key to the tribal vote.
The importance of tribal leaders stems partly from the fact that during apartheid there was a tendency to romanticise African life before colonialism "when we were governed by our own kings". The tribal leadership therefore embodied our lost nationhood and were a living reminder of "past glories". To some it seemed fitting that the abolition of apartheid oppression should be sealed by the restoration of the dignity of our kings. Their humiliation by colonialists had symbolized our oppression.